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Author

Martin Wrulich

Bio: Martin Wrulich is an academic researcher from Vienna University of Technology. The author has contributed to research in topics: MIMO & Telecommunications link. The author has an hindex of 17, co-authored 38 publications receiving 1885 citations.

Papers
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Proceedings ArticleDOI
16 May 2010
TL;DR: A MATLAB computationally efficient LTE system level simulator capable of evaluating the performance of the Downlink Shared Channel of LTE SISO and MIMO networks using Open Loop Spatial Multiplexing and Transmission Diversity transmit modes is presented.
Abstract: In order to evaluate the performance of new mobile network technologies, system level simulations are crucial. They aim at determining whether, and at which level predicted link level gains impact network performance. In this paper we present a MATLAB computationally efficient LTE system level simulator. The simulator is offered for free under an academic, noncommercial use license, a first to the authors' knowledge. The simulator is capable of evaluating the performance of the Downlink Shared Channel of LTE SISO and MIMO networks using Open Loop Spatial Multiplexing and Transmission Diversity transmit modes. The physical layer model is based on the postequalization SINR and provides the simulation pre-calculated "fading parameters" representing each of the individual interference terms. This structure allows the fading parameters to be pregenerated offline, vastly reducing computational complexity at run-time.

578 citations

Proceedings ArticleDOI
24 Aug 2009
TL;DR: This paper presents a MATLAB-based downlink physical-layer simulator for LTE that can efficiently be executed on multi-core processors to significantly reduce the simulation time.
Abstract: Research and development of signal processing algorithms for UMTS Long Term Evolution (LTE) requires a realistic, flexible, and standard-compliant simulation environment. To facilitate comparisons with work of other research groups such a simulation environment should ideally be publicly available. In this paper, we present a MATLAB-based downlink physical-layer simulator for LTE. We identify different research applications that are covered by our simulator. Depending on the research focus, the simulator offers to carry out single-downlink, single-cell multi-user, and multi-cell multi-user simulations. By utilizing the Parallel Computing Toolbox of MATLAB, the simulator can efficiently be executed on multi-core processors to significantly reduce the simulation time.

515 citations

Journal ArticleDOI
TL;DR: This study explains how link and system level simulations are connected and shows how the link level simulator serves as a reference to design the system level simulator, and compares the accuracy of the PHY modeling at system level by means of simulations performed both with bit-accurate link level simulations and PHY-model-based systemlevel simulations.
Abstract: In this article, we introduce MATLAB-based link and system level simulation environments for UMTS Long-Term Evolution (LTE). The source codes of both simulators are available under an academic non-commercial use license, allowing researchers full access to standard-compliant simulation environments. Owing to the open source availability, the simulators enable reproducible research in wireless communications and comparison of novel algorithms. In this study, we explain how link and system level simulations are connected and show how the link level simulator serves as a reference to design the system level simulator. We compare the accuracy of the PHY modeling at system level by means of simulations performed both with bit-accurate link level simulations and PHY-model-based system level simulations. We highlight some of the currently most interesting research questions for LTE, and explain by some research examples how our simulators can be applied.

292 citations

Proceedings ArticleDOI
29 Apr 2010
TL;DR: The proposed method provides means to obtain the number of useful MIMO transmission layers, signaled in form of the Rank indicator (RI), by maximizing mutual information also with respect to this value.
Abstract: This paper presents an efficient method for calculating the Precoding Matrix Indicator (PMI) at the receiver. The PMI is required for MIMO precoding in the downlink of a 3GPP UMTS/LTE system. Our method is based on maximizing the mutual information between the transmitted and received symbols with respect to the precoding matrix applied at the transmitter. The advantage of this method is that it is independent of the symbol alphabet (4/16/64 QAM) and code rate applied, which are signaled by the channel quality indicator (CQI). Although this paper only focuses on the selection of the optimal PMI, such a procedure eventually allows to decouple both problems (CQI and PMI calculation), thereby reducing complexity. The proposed method also provides means to obtain the number of useful MIMO transmission layers, signaled in form of the Rank indicator (RI), by maximizing mutual information also with respect to this value. The performance of the method is evaluated utilizing an LTE downlink physical-layer simulator.

76 citations

01 Jan 2009
TL;DR: This paper proposes a low-complexity model based on AWGN link level simulations that is capable of reliably predicting the BLER improvement due to the use of incremental redundancy H-ARQ in LTE.
Abstract: The 3rd Generation Partnership Project (3GPP)’s Release’8 Long Term Evolution (LTE) defines the next step of 3G technology. LTE offers significant improvements over previous technologies such as UMTS/HSPA. Higher downlink and uplink speeds, lower latency and simpler network architecture are among the new features that are provided. One of the central features that provides transmission robustness is hybridARQ, which in LTE provides physical layer retransmission using incremental redundancy and soft combining. In this paper we propose a low-complexity model based on AWGN link level simulations that is capable of reliably predicting the BLER improvement due to the use of incremental redundancy H-ARQ in LTE.

67 citations


Cited by
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Journal ArticleDOI
TL;DR: A tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association policies is developed and the average ergodic rate of the typical user, and the minimum average users throughput - the smallest value among the average user throughputs supported by one cell in each tier is derived.
Abstract: In this paper we develop a tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association policies. The HCN is modeled as a multi-tier cellular network where each tier's base stations (BSs) are randomly located and have a particular transmit power, path loss exponent, spatial density, and bias towards admitting mobile users. For example, as compared to macrocells, picocells would usually have lower transmit power, higher path loss exponent (lower antennas), higher spatial density (many picocells per macrocell), and a positive bias so that macrocell users are actively encouraged to use the more lightly loaded picocells. In the present paper we implicitly assume all base stations have full queues; future work should relax this. For this model, we derive the outage probability of a typical user in the whole network or a certain tier, which is equivalently the downlink SINR cumulative distribution function. The results are accurate for all SINRs, and their expressions admit quite simple closed-forms in some plausible special cases. We also derive the average ergodic rate of the typical user, and the minimum average user throughput - the smallest value among the average user throughputs supported by one cell in each tier. We observe that neither the number of BSs or tiers changes the outage probability or average ergodic rate in an interference-limited full-loaded HCN with unbiased cell association (no biasing), and observe how biasing alters the various metrics.

1,140 citations

01 Feb 2009

911 citations

Journal ArticleDOI
TL;DR: The open-source framework LTE-Sim is presented to provide a complete performance verification of LTE networks and has been conceived to simulate uplink and downlink scheduling strategies in multicell/multiuser environments, taking into account user mobility, radio resource optimization, frequency reuse techniques, the adaptive modulation and coding module, and other aspects that are very relevant to the industrial and scientific communities.
Abstract: Long-term evolution (LTE) represents an emerging and promising technology for providing broadband ubiquitous Internet access. For this reason, several research groups are trying to optimize its performance. Unfortunately, at present, to the best of our knowledge, no open-source simulation platforms, which the scientific community can use to evaluate the performance of the entire LTE system, are freely available. The lack of a common reference simulator does not help the work of researchers and poses limitations on the comparison of results claimed by different research groups. To bridge this gap, herein, the open-source framework LTE-Sim is presented to provide a complete performance verification of LTE networks. LTE-Sim has been conceived to simulate uplink and downlink scheduling strategies in multicell/multiuser environments, taking into account user mobility, radio resource optimization, frequency reuse techniques, the adaptive modulation and coding module, and other aspects that are very relevant to the industrial and scientific communities. The effectiveness of the proposed simulator has been tested and verified considering 1) the software scalability test, which analyzes both memory and simulation time requirements; and 2) the performance evaluation of a realistic LTE network providing a comparison among well-known scheduling strategies.

685 citations

Proceedings ArticleDOI
16 May 2010
TL;DR: A MATLAB computationally efficient LTE system level simulator capable of evaluating the performance of the Downlink Shared Channel of LTE SISO and MIMO networks using Open Loop Spatial Multiplexing and Transmission Diversity transmit modes is presented.
Abstract: In order to evaluate the performance of new mobile network technologies, system level simulations are crucial. They aim at determining whether, and at which level predicted link level gains impact network performance. In this paper we present a MATLAB computationally efficient LTE system level simulator. The simulator is offered for free under an academic, noncommercial use license, a first to the authors' knowledge. The simulator is capable of evaluating the performance of the Downlink Shared Channel of LTE SISO and MIMO networks using Open Loop Spatial Multiplexing and Transmission Diversity transmit modes. The physical layer model is based on the postequalization SINR and provides the simulation pre-calculated "fading parameters" representing each of the individual interference terms. This structure allows the fading parameters to be pregenerated offline, vastly reducing computational complexity at run-time.

578 citations

Proceedings ArticleDOI
24 Aug 2009
TL;DR: This paper presents a MATLAB-based downlink physical-layer simulator for LTE that can efficiently be executed on multi-core processors to significantly reduce the simulation time.
Abstract: Research and development of signal processing algorithms for UMTS Long Term Evolution (LTE) requires a realistic, flexible, and standard-compliant simulation environment. To facilitate comparisons with work of other research groups such a simulation environment should ideally be publicly available. In this paper, we present a MATLAB-based downlink physical-layer simulator for LTE. We identify different research applications that are covered by our simulator. Depending on the research focus, the simulator offers to carry out single-downlink, single-cell multi-user, and multi-cell multi-user simulations. By utilizing the Parallel Computing Toolbox of MATLAB, the simulator can efficiently be executed on multi-core processors to significantly reduce the simulation time.

515 citations