Interference Mitigation by Practical Transmit Beamforming Methods in Closed Femtocells

Husso, Mika; Hämäläinen, Jyri; Jäntti, Riku; Li, Juan; Mutafungwa, Edward; Wichman, Risto; Zheng, Zhong; Wyglinski, Alexander M.

doi:10.1155/2010/186815

Cited by 22 publications

(9 citation statements)

References 25 publications

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“…Note that the spatial‐domain may also be used to manage interference in Het‐Nets. For example, the authors of proposed to use practical transmit beamforming methods to mitigate interference in closed‐access femtocellular environments.…”

Section: Introductionmentioning

confidence: 99%

Interference management for LTE‐Advanced Het‐Nets: stochastic scheduling approach in frequency domain

Zheng

Dowhuszko

Hämäläinen

2012

Trans. Emerging Tel. Tech.

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Heterogeneous networks represent a practical way to face high traffic demands in densely populated areas. Nevertheless, to achieve these advertised data rates, advanced interference management techniques are required. Trying to tackle this problem, this paper presents a stochastic scheduling approach for two-layer LTE-Advanced networks. The proposed stochastic frequency-domain scheduling (SFDS) algorithm seeks the avoidance of cross-layer and colayer interference, and is based on allocating different portions of the transmission bandwidth probabilistically. The SFDS algorithm is first presented as an interference management solution for an orthogonal frequency-division multiple access system (i.e. LTE-Advanced downlink). Later on, the SFDS algorithm is extended to be compatible with single-carrier frequency-division multiple access transmissions, and its performance is evaluated when combined with open-loop power control techniques (i.e. LTE-Advanced uplink). Extensive system level simulations are carried out to evaluate the performance of SFDS algorithm in a predefined LTE-Advanced scenario that combines both macrolayer and femtolayer. Results show that the proposed algorithm allows to balance the cross-layer and colayer interferences, extending the performance trade-offs that well-known full-range spectrum allocation and orthogonal spectrum allocation approaches provide.

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Section: Introductionmentioning

confidence: 99%

Interference management for LTE‐Advanced Het‐Nets: stochastic scheduling approach in frequency domain

Zheng

Dowhuszko

Hämäläinen

2012

Trans. Emerging Tel. Tech.

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“…In, e.g., [8,9], the authors http://jwcn.eurasipjournals.com/content/2012/1/293 proposed the use of dynamic frequency re-use, whereas in [10,11] power control was utilized for downlink and uplink cross-layer interference mitigation purposes, respectively. In addition, contributions of [12][13][14] explored the use of transmit beamforming (TBF) methods for interference mitigation that rely on explicit channel state information (CSI) reports in the reverse channel (i.e., for FDD air interfaces), while [15] analyzed the use of a busy burst protocol to coordinate the selection of TBF vectors at neighboring cells when channel reciprocity holds (i.e., for TDD air interfaces). In [16], a scheduling method was presented for reducing macro-femto interference, and in [17,18] beamforming and scheduling were combined for inter-femtocell interference mitigation purposes.…”

Section: Introductionmentioning

confidence: 99%

Combined transmit beamforming and channel-aware scheduling for interference mitigation in femtocells

Dowhuszko

Husso

Hämäläinen

2012

J Wireless Com Network

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The introduction of femtocells in mobile networks gives rise to new co-layer and crosslayer interference scenarios. To mitigate interference, several approaches have been proposed in the literature including, e.g., transmit beamforming (TBF), power control, and fractional frequency reuse. In this article, we present an interference mitigation approach that relies on a low-rate control channel between the victim terminal and the interfering femto access point (FAP). The proposed method combines both, practical TBF schemes and simple one-bit channel-aware scheduling algorithms. We show that the proposed method can be effectively used not only to mitigate interference among FAPs, but also to balance user rates in adjacent cells with small signaling overhead.

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“…In enterprise femtocell deployments, due to the single-path slow fading indoor channel, a user equipment (UE) may experience frequent hard handovers (HHO) when in the boundary region of two neighboring femtocells 1 . Each HHO can result in several consecutive frame erasures, which can cause a noticeable voice artifact (NVA).…”

Section: Introductionmentioning

confidence: 99%

“…Hence frequent HHOs can lead to noticeable degradation of user experience. Inter-femto soft handover (SHO) can mitigate this issue by providing 1 Since a large portion of UEs currently do not support Rx diversity, we assume absence of Rx diversity at the UE throughout this paper. independent fading on each SHO leg and provide excellent voice quality.…”

Section: Introductionmentioning

confidence: 99%

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Benefits of transmit and receive diversity in enterprise femtocell deployments

Jiang

Zhou

Anand

et al. 2011

2011 International Symposium of Modeling and Optimization of Mobile, Ad Hoc, and Wireless Networks

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In this paper, we study the benefits of transmit and receive diversity for enterprise UMTS femtocell deployments. Indoor enterprise femtocell deployments face a single-path slow fading wireless environment that may lead to frequent hard handovers in the boundary region of neighboring femtocells and consequent degradation in the voice quality experienced by the users. In the absence of soft-handover (SHO) support, transmit diversity at the femtocell can combat single-path fading channel. We demonstrate through over-the-air tests that transmit diversity is very effective in reducing the number of hard handovers and therefore results in significant improvement in voice quality for enterprise users. On the uplink, we study system stability using an analytical approach. We derive analytical conditions for system stability with and without receive diversity at the femtocells. Using this analytical framework, benefits of receive diversity in maintaining system stability and preventing uplink power racing between neighboring femtocells are quantified. It is shown that, in the absence of SHO, receive diversity is very effective in maintaining system stability by preventing potential uplink power racing caused by inter-femto interference.

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Interference Mitigation by Practical Transmit Beamforming Methods in Closed Femtocells

Cited by 22 publications

References 25 publications

Interference management for LTE‐Advanced Het‐Nets: stochastic scheduling approach in frequency domain

Interference management for LTE‐Advanced Het‐Nets: stochastic scheduling approach in frequency domain

Combined transmit beamforming and channel-aware scheduling for interference mitigation in femtocells

Benefits of transmit and receive diversity in enterprise femtocell deployments

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