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We consider smart “cognitive” femtocells, that can decode the base station control channel and make decision on their transmission opportunities based on the scheduling and resource allocation of the overlaying macrocell. The operation of such femtocells is somehow reminiscent of “Type II” relays, as specified in the IEEE 802.16j standard. Under certain system assumptions, we consider the tradeoff...
In this paper, we propose a new dynamic frequency assignment scheme for femtoCells in OFDMA networks. The femtoCell base stations are small cellular base stations specially designed to improve the poor indoor coverage and increase the system capacity for cellular and wireless broadband networks. However, these femto-base stations cause harmful interference to the macroCells. Therefore, the optimization...
In this paper we discuss some of the benefits and challenges of deploying femtocells in a cellular network. In particular, we focus on the tradeoff between energy efficiency and system performance. With realistic LTE system parameters, we have shown that femtocells can indeed improve energy efficiency of the network. However, this comes with a price - performance degradation due to interference, which...
Femtocell is one of promising key technologies to increase the efficiency and coverage of next generation broadband wireless networks. However, there exists interference problem between femtocells and macrocell due to co-channel operation. In this paper, we propose an efficient frequency resource allocation scheme for newly deployed femtocells in the legacy OFDMA networks in order to maximize the...
Cognitive radio and femtocells are recent technology breakthroughs that aim at achieving throughput improvement by means of spectrum management and interference mitigation, respectively. However, these technologies are limited by the former's susceptibility to interference and the latter's dependence on bandwidth availability. In this paper, we overcome these limitations by integrating cognitive radio...
This paper presents a framework based on self-organization to jointly self-optimize the spectrum assignment and the transmission power in the context of downlink OFDMA femtocell deployments. It is a distributed framework where each femtocell acts as an autonomous entity. Femtocells perform spectrum and transmission power assignment based on users' reported measurements, which are employed to sense...
This work presents a novel approach for the avoidance of cross-tier interference in two-tier networks comprised of Orthogonal Frequency Division Multiple Access (OFDMA) macrocells and femtocells. This new technique is based on the use of Intracell HandOvers (IHOs), and it makes possible that either a macrocell or a femtocell can reassign its sub-channel or power allocation upon the detection of cross-tier...
Femtocell has been considered by the wireless industry as a promising solution not only to improve indoor coverage, but also to unload traffic from overburdened macrocell networks. In hybrid macro/femto networks, macrocells may have to share the same spectrum with femtocells, due to spectrum availability and network infrastructure considerations, in spite of potentially excessive interference caused...
Femtocells have the potential to provide significant benefits for cellular users. However, the introduction of femtocells also introduces new sources of interference for existing users. In this paper, three techniques for interference mitigation using MIMO precoding are considered at the femtocellular base stations to reduce the interference to the macrocellular users: Precoding Matrix Index (PMI)...
A dynamic system level simulator for LTE networks was developed for investigating the interference behaviour of femtocells placed within macrocells. We simulate a multi-cell, multi-user and multi-carrier system in the downlink for Single-Input, Single-Output (SISO) and Multiple-Input, Multiple-Output (MIMO) antenna configurations.
Femtocells are receiving considerable interest in mobile communications as a strategy to overcome the indoor coverage problems as well as to improve the efficiency of current macrocell systems. One of the most critical issues in femtocells is the potential interference between nearby femtocells and from femtocells to macrocells or to mobile handsets. In this work, we illustrate some decentralized...
Femtocells or home base stations are a proposed solution to the problem of degraded indoor service from the macrocell base station in future 4G data networks. In this paper, we study user incentives for the adoption of femtocells and their resulting impact on network operator revenues. We model a monopolist network operator who offers the option of macrocell access or macro+femtocell access to a population...
Femtocells are a promising solution for the provision of high indoor coverage and capacity. Furthermore, OFDMA-based femtocells have proven to be highly versatile when dealing with cross-layer co-channel interference thanks to the allocation of frequency subchannels. However, concerns still exist related to the impact of the different access methods to femtocells in an overlayed network. Femtocells...
Femtocells are low-cost, low-power cellular base stations that are designed to provide high quality cellular service in residential or enterprise environments and operate in licensed spectrum to connect conventional, unmodified mobile terminals to a mobile operator's network. The deployment of femtocells will reduce the number of indoor users that need to be served by the macrocellular network. Moreover,...
Femtocells are low-cost, miniature base-stations intended to improve indoor coverage in 3G networks and beyond. One of the main issues in adopting femtocells en masse is the surge in interference to the mobile users served by the macrocell arising from unplanned networks and private access. Therefore, distributed power control mechanisms for femtocells are essential to shield the existing users of...
Femtocells have been recently proposed as a potential good solution to increase not only indoor radio coverage, but also system capacity. In this paper, a framework for radio coverage prediction and system level simulation for WiMAX macrocell/femtocell scenarios is presented. Furthermore, the feasibility of the co-channel deployment of WiMAX femtocell in an existing WiMAX macrocell network is investigated,...
Two-tier networks, comprising a conventional cellular network overlaid with shorter range hotspots (e.g. femtocells, distributed antennas, or wired relays), offer an economically viable way to improve cellular system capacity. The capacity-limiting factor in such networks is interference. The cross-tier interference between macrocells and femtocells can suffocate the capacity due to the near-far problem,...
Successful deployment of femtocells requires intelligent cell planning and introduces some unique challenges. In this letter, an efficient frequency assignment technique is proposed for femtocells considering practical issues such as hand-off, coverage, and interference. Moreover, interference-limited coverage area (ILCA) of a co-channel femtocell base station is calculated based on parameters such...
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