• Title/Summary/Keyword: Interference Mitigation

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QoS Priority Based Femtocell User Power Control for Interference Mitigation in 3GPP LTE-A HetNet

  • Ahmad, Ishtiaq;Kaleem, Zeeshan;Chang, KyungHi
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39B no.2
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    • pp.61-74
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    • 2014
  • In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.

Low-Complexity Distributed Algorithms for Uplink CoMP in Heterogeneous LTE Networks

  • Annavajjala, Ramesh
    • Journal of Communications and Networks
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    • v.18 no.2
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    • pp.150-161
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    • 2016
  • Coordinated multi-point transmission (CoMP) techniques are being touted as enabling technologies for interference mitigation in next generation heterogeneous wireless networks (HetNets). In this paper, we present a comparative performance study of uplink (UL) CoMP algorithms for the 3GPP LTE HetNets. Focusing on a distributed and functionally-split architecture, we consider six distinct UL-CoMP algorithms: 1. Joint reception in the frequency-domain (JRFD) 2. Two-stage equalization (TSEQ) 3. Log-likelihood ratio exchange (LLR-E) 4. Symmetric TSEQ (S-TSEQ) 5. Transport block selection diversity (TBSD) 6. Coordinated scheduling with adaptive interference mitigation (CS-AIM) where JRFD, TSEQ, S-TSEQ, TBSD and CS-AIM are our main contributions in this paper, and quantify their relative performances via the post-processing signal-to-interference-plus-noise ratio distributions.We also compare the CoMP-specific front-haul rate requirements for all the schemes considered in this paper. Our results indicate that, with a linear minimum mean-square error receiver, the JRFD and TSEQ have identical performances, whereas S-TSEQ relaxes the front-haul latency requirements while approaching the performance of TSEQ. Furthermore, in a HetNet environment, we find that CS-AIM provides an attractive alternative to TBSD and LLR-E with a significantly reduced CoMP-specific front-haul rate requirement.

Performance of Interference Mitigation for Visible Light Communi cation System (가시광 통신 시스템의 간섭 완화 성능)

  • Park, In-Hwan;Kim, Yoon-Hyun;Kim, Jin-Young
    • Journal of Satellite, Information and Communications
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    • v.6 no.1
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    • pp.57-62
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    • 2011
  • The VLC (visible light communication) system is communication technology using visible rays (RGB) that come out in LED device. It is energy curtailment effect and possible in ubiquitous network service applications. Also, VLC system has the above advantage about that the communication throughout the whole room is enabled by high power lighting and lighting equipment with white colored LED which are easy to install and have good outward appearance. However, the signal detection performance for the receiver near the network of transmitter boundary is severely degraded and the transmission efficiency decreased due to the influence of the interference signal from the adjacent networks. In this paper, we propose an interference mitigation method with optical beamforming in VLC systems, and evaluate the reception performance. For the system BER, the proposed optical beamforming transmission demonstrates the performance enhancement compared to the not using the optical beamforming scheme, and up to about 5~6dB SNR performance gain is achieved.

Performance of Interference Mitigation using Optical Relay and Optical Beamforming in Visible Light Communication Systems (가시광 통신 시스템에서 Optical Relay와 Optical Beamforming을 통한 간섭 완화 성능)

  • Hwang, Yu Min;Kim, Yoon Hyun;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • v.7 no.3
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    • pp.63-68
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    • 2012
  • The VLC (visible light communication) system is communication technology using visible rays (RGB) that come out in LED device. It is energy curtailment effect and possible in ubiquitous network service applications. Also, VLC system has the above advantage about that the communication throughout the whole room is enabled by high power lighting and lighting equipment with white colored LED which are easy to install and have good outward appearance. However, the signal detection performance for the receiver near the network of transmitter boundary is severely degraded and the transmission efficiency decreased due to the influence of the interference signal from the adjacent networks. In this paper, we propose an interference mitigation method with optical relay and optical beamforming scheme in VLC systems, and evaluate the reception performance. For the system BER, the proposed system demonstrates the performance enhancement compared to the not using the optical relay and optical beamforming scheme, and SNR performance gain and higher channel capacity is achieved.

Pilot Interference Cancellation in a WCDMA Wireless Repeater (WCDMA 무선 중계기에서 파일럿 간섭제거)

  • Kim, Sun-Ho;Im, Sung-Bin;Lee, Jae-Jin
    • Proceedings of the IEEK Conference
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    • 2008.06a
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    • pp.307-308
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    • 2008
  • In this paper, we propose a mitigation method to reduce the effect of pilot interference at the wireless repeater. This improves the signal to interference ratio (SIR), and enables increased cell capacity and better bits error rates (BER) performance in the WCDMA systems. Simulation studies have been carried out to verify the proposed approach and we obtained promising results.

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Interference Analysis and Its Mitigation Policy Based on MAC Layer for Peaceful Co-Existence between Unlicensed Devices (비면허 기기 간 주파수 공동사용을 위한 MAC 계층 기반의 간섭 분석 및 간섭 완화 정책)

  • Jang, Byung-Jun;Choi, Sunwoong;Yoon, Hyungoo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.8
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    • pp.841-848
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    • 2013
  • In order for unlicensed devices to co-exist on the same frequency band, the frequency interference mitigation policy is necessary. Because the effects of frequency interference between unlicensed devices may vary depending on the analysis layer, exact interference analysis must be proceeded before making any related spectrum policy. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band were analyzed in the physical layer and MAC layer, respectively. From the results, we confirmed that the interference analysis in MAC layer is closer to the measured results. Based on these investigations, we suggest a new co-existence criterion for unlicensed devices in MAC layer.

An Efficient Inter-Cell Interference Mitigation Scheme for Proximity Service in Cellular Networks (셀룰러 망에서 Proximity Service를 위한 효율적인 셀 간 간섭 완화 방안)

  • Kim, Cha-Ju;Min, Sang-Won
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.17 no.1
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    • pp.100-113
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    • 2018
  • The Proximity Service, which is one of the most popular network capacity improvement methods, uses the frequency reuse in order to increase the frequency efficiency. As a result, inter-cell interference between cellular and proximity service users occurs at a cell edge. In this paper, we proposed a mitigation scheme for inter-cell interference, where we suggested a new function of and eNB with ProSe function exchanging information about ProSe parameters and ProSe user equipment with neighboring cells via the X2 interface. As the first step, the resource which did not cause the inter-cell interference problem were pre-allocated through the frequency sensing in the ProSe direct discovery. As the next step, the inter-cell interference problem was solved by reallocating appropriate resources based on the ProSe application code, the ProSe application QoS, the ProSe application ID and validity timer in ProSe direct communication.

Staggered Resource Allocation Scheme for Co-Channel Interference Mitigation in a Cellular OFDMA System (셀룰러 OFDMA 시스템에서 동일 채널 간섭 완화를 위한 대역 분산적 자원 할당 기법)

  • Son, Jun-Ho;Min, Tae-Young;Kang, Chung-G.
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12A
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    • pp.1191-1199
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    • 2008
  • We propose the Staggered-zone Resource Allocation (SRA) in order to relax throughput decrease problems by the co-channel interference of the cell boundary users at the cellular OFDMA system using frequency reuse factor K=1 and analyze the throughput improvement. The proposed algorithm allocates the resources to the users in compliance with resource allocation rule which is planned in order to minimize co-channel interference between cells without any additional information. The resource allocation method in the SRA lines up the users in pathloss order as descending series, and then allocates from pre-determined resource allocation region where decides differently in each cell. This algorithm prevents the co-channel interferences of the cell boundary user to be caused by using same resource simultaneously and equalizes interference to the users in the cell.

Interference Management with Block Diagonalization for Macro/Femto Coexisting Networks

  • Jang, Uk;Cho, Kee-Seong;Ryu, Won;Lee, Ho-Jin
    • ETRI Journal
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    • v.34 no.3
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    • pp.297-307
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    • 2012
  • A femtocell is a small cellular base station, typically designed for use in a home or small business. The random deployment of a femtocell has a critical effect on the performance of a macrocell network due to co-channel interference. Utilizing the advantage of a multiple-input multiple-output system, each femto base station (FBS) is able to form a cluster and generates a precoding matrix, which is a modified version of conventional single-cell block diagonalization, in a cooperative manner. Since interference from clustered-FBSs located at the nearby macro user equipment (MUE) is the dominant interference contributor to the coexisting networks, each cluster generates a precoding matrix considering the effects of interference on nearby MUEs. Through simulation, we verify that the proposed algorithm shows better performance respective to both MUE and femto user equipment, in terms of capacity.

Enhanced Spatial Covariance Matrix Estimation for Asynchronous Inter-Cell Interference Mitigation in MIMO-OFDMA System (3GPP LTE MIMO-OFDMA 시스템의 인접 셀 간섭 완화를 위한 개선된 Spatial Covariance Matrix 추정 기법)

  • Moon, Jong-Gun;Jang, Jun-Hee;Han, Jung-Su;Kim, Sung-Soo;Kim, Yong-Serk;Choi, Hyung-Jin
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.5C
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    • pp.527-539
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    • 2009
  • In this paper, we propose an asynchonous ICI (Inter-Cell Interference) mitigation techniques for 3GPP LTE MIMO-OFDMA down-link receiver. An increasing in symbol timing misalignments may occur relative to sychronous network as the result of BS (Base Station) timing differences. Such symbol synchronization errors that exceed the guard interval or the cyclic prefix duration may result in MAI (Multiple Access Interference) for other carriers. In particular, at the cell boundary, this MAI becomes a critical factor, leading to degraded channel throughput and severe asynchronous ICI. Hence, many researchers have investigated the interference mitigation method in the presence of asynchronous ICI and it appears that the knowledge of the SCM (Spatial Covariance Matrix) of the asynchronous ICI plus background noise is an important issue. Generally, it is assumed that the SCM estimated by using training symbols. However, it is difficult to measure the interference statistics for a long time and training symbol is also not appropriate for MIMO-OFDMA system such as LTE. Therefore, a noise reduction method is required to improve the estimation accuracy. Although the conventional time-domain low-pass type weighting method can be effective for noise reduction, it causes significant estimation error due to the spectral leakage in practical OFDM system. Therefore, we propose a time-domain sinc type weighing method which can not only reduce the noise effectively minimizing estimation error caused by the spectral leakage but also implement frequency-domain moving average filter easily. By using computer simulation, we show that the proposed method can provide up to 3dB SIR gain compared with the conventional method.