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ABSTRACT: Carrier aggregation is one of the key features for LTE-Advanced. By means of CA, users gain access to a total bandwidth of up to 100 MHz in order to meet the IMT-Advanced requirements. The system bandwidth may be contiguous, or composed of several non-contiguous bandwidth chunks that are aggregated. This article presents a summary of the supported CA scenarios as well as an overview of the CA functionality for LTE-Advanced with special emphasis on the basic concept, control mechanisms, and performance aspects. The discussion includes definitions of the new terms primary cell (PCell) and secondary cell (SCell), mechanisms for activation and deactivation of CCs, and the new cross-CC scheduling functionality for improved control channel optimizations. We also demonstrate how CA can be used as an enabler for simple yet effective frequency domain interference management schemes. In particular, interference management is anticipated to provide significant gains in heterogeneous networks, envisioning intrinsically uncoordinated deployments of home base stations.
IEEE Communications Magazine 07/2011; · 3.79 Impact Factor
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ABSTRACT: The recent introduction of carrier aggregation in LTE-Advanced enables new possibilities in designing frequency domain interference reduction and management schemes. These methodologies are of extreme interest in the case of dense and uncoordinated deployments of femtocells. In such scenarios, dense deployment of cells coupled with the scarcity of frequency resources may lead to a potentially disruptive amount of interference, which severely affects the performance of the system. This contribution presents a novel method inspired by graph and coalitional game theories. The proposed algorithm consists of a set of distributed and scalable rules for building coalitions; these rules essentially resolve the conflicts among avid femtocells competing for a limited amount of resources. The proposed scheme has been designed by targeting localized reconfigurations, thus avoiding reconfiguration storms in the network. Furthermore, the rules governing the resource redistribution ensure overall system performance improvements while maintaining a certain degree of fairness among the competing nodes. Simulation results prove the effectiveness of the proposed method.
Global Telecommunications Conference (GLOBECOM 2010), 2010 IEEE; 01/2011
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ABSTRACT: Uncoordinated deployment of eNBs in local area environments will benefit from having support for dynamic frequency re-use mechanisms also known as "autonomous component carrier selection", where each eNB dynamically selects to use only a subset of the available component carriers (i.e. using from one component carrier up to the maximum number of available component carriers). Component carriers are selected autonomously by each eNB depending on the offered traffic, interference coupling with neighboring cells, etc. In this contribution we propose a simple and distributed scheme based on so-called background interference matrices (BIMs) for autonomous component carrier selection. Extensive numerical simulation campaigns indicate that the proposed scheme effectively allows each eNB to select the most attractive frequency configuration; improving average user capacity and boosting cell edge performance considerably.
Vehicular Technology Conference Fall (VTC 2009-Fall), 2009 IEEE 70th; 10/2009
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ABSTRACT: Low-power base stations such as femtocells are one of the candidates for high-data-rate provisioning in local areas, such as residences, apartment complexes, business offices, and outdoor hotspot scenarios. Unfortunately, the benefits are not without new challenges in terms of interference management and efficient system operation. Due to the expected large number of user-deployed cells, centralized network planning becomes impractical, and new scalable alternatives must be sought. In this article we propose a fully distributed and scalable solution to the interference management problem in local areas, basing our study case on LTE-Advanced. We present extensive network simulation results to demonstrate that a simple and robust interference management scheme, called autonomous component carrier selection, allows each cell to select the most attractive frequency configuration; improving the experience of all users and not just the few best ones, while overall cell capacity is not compromised.
IEEE Communications Magazine 10/2009; · 3.79 Impact Factor
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ABSTRACT: We analyse the downlink (DL) cell throughput for a WCDMA system using switched beamforming (SBF) with 4-element antenna array at the base station (node-B) and dual antenna (2Rx) user equipment (UE). We investigate the performance as a function of the penetration rate of 2Rx UEs. The performance assessment is conducted with dynamic system simulations, which are supplemented with simple theoretical analysis. Code blocking (CB) occurs when a UE is denied access in the cell due to lack of a DL channelisation code under the primary scrambling code for that cell. When the code-blocking problem is circumvented, it is observed from the simulation results that at 100% penetration rate of 2Rx UEs, the combined feature offers more than the multiplicative gain in the capacity improvement. The numerical result obtained from the theoretical analysis complements the simulation results. The SBF-2Rx code-unrestricted (CU) capacity gain is 327% compared to a 3-sector single directional antenna transmission at the node-B and single antenna reception at the UE
Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd; 06/2006
