Cellular networks are an essential part of todays communication infrastructure. The ever-increasing demand for higher data-rates calls for a close cooperation between researchers and industry/standardization experts which hardly exists in practice. In this article we give an overview about our efforts in trying to bridge this gap. Our research group provides a standard-compliant open-source simulation platform for 3GPP LTE that enables reproducible research in a well-defined environment. We demonstrate that much innovative research under the confined framework of a real-world standard is still possible, sometimes even encouraged. With examplary samples of our research work we investigate on the potential of several important research areas under typical practical conditions.Comment: The final version of the manuscript is available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6514821&isnumber=633654
System-level simulations have become an indispensable tool for predicting the behavior of wireless cellular systems. As exact link-level modeling is unfeasible due to its huge complexity, mathematical abstraction is required to obtain equivalent results by less complexity. A particular problem in such approaches is the modeling of multiple coherent transmissions. Those arise in multiple-input-multipleoutput transmissions at every base station but nowadays so-called coordinated multipoint (CoMP) techniques have become very popular, allowing to allocate two or more spatially separated transmission points. Also, multimedia broadcast single frequency networks (MBSFNs) have been introduced recently in long-term evolution (LTE), which enables efficient broadcasting transmission suitable for spreading information that has a high user demand as well as simultaneously sending updates to a large number of devices. This paper introduces the concept of runtime-precoding, which allows to accurately abstract many coherent transmission schemes while keeping additional complexity at a minimum. We explain its implementation and advantages. For validation, we incorporate the runtime-precoding functionality into the Vienna LTE-A downlink systemlevel simulator, which is an open source tool, freely available under an academic noncommercial use license. We measure simulation run times and compare them against the legacy approach as well as link-level simulations. Furthermore, we present multiple application examples in the context of intrasite and intersite CoMP for train communications and MBSFN.INDEX TERMS Link abstraction, link quality model, runtime-precoding, 3GPP, LTE-A, Vienna LTE-A downlink system level simulator, MIESM, Vienna LTE-A downlink link level simulator, LTE transmission modes, coordinated multipoint, multimedia broadcast single frequency networks, high-user mobility.
Massive MIMO and 3D beamforming have been identified as key technologies for future mobile cellular networks. Their investigation requires channel models that consider not only the azimuth-but also the elevation direction. Recently, the 3rd Generation Partnership Project (3GPP) has released a new 3D spatial channel model. It supports planar antenna arrays and enables to scrutinize concepts such as elevation beamforming and full dimension MIMO. A particular challenge is the practical implementation of the model. Dealing with enormous computational complexity requires to design a highly efficient approach. This paper provides a guideline for the practical implementation of the 3GPP 3D model into existing link-and system-level simulation tools. Considering the complexity of the model itself, our main focus is on computational efficiency. We present simulation examples using the proposed procedure with the Vienna LTE-A Downlink System Level Simulator. We measure simulation run times with respect to various network parameters. Our results allow to quantify the increase in complexity, when accounting for the elevation dimension. Moreover, they exhibit general trends when considering a large number of antenna elements per antenna array. We also draw a comparison with the WINNER channel model, which represents the most closely related channel model in 2D.
Abstract-The demand for a broadband wireless connection is nowadays no longer limited to stationary situations, but also required while traveling. Therefore, there exist combined efforts to provide wireless access also on High Speed Trains (HSTs), in order to add to the attractiveness of this means for transportation. Installing an additional relay on the train, to facilitate the communication, is an approach that has already been extensively discussed in literature. The possibility of a direct communication between the base station and the passenger has been neglected until now, despite it having numerous advantages. Therefore, a comparison between these two opposing approaches is presented in this paper, accompanied by a detailed discussion of the related aspects. The focus is set on the feasibility of the direct link approach, including simulation results. Further technical issues are also presented, especially regarding the interdependencies of the different aspects and providing a view of mobile-and train-operators on the topic.
Beamforming and Multiple Input Multiple Output (MIMO) have been identified as key technologies to meet the ever increasing capacity demands in future mobile cellular networks. So far, these features have mainly been investigated in the azimuth dimension, considering one-dimensional antenna arrays. Recently, the 3rd Generation Partnership Project has released a new 3-dimensional (3D) spatial channel model that also accounts for the elevation. It supports two-dimensional antenna arrays and enables to scrutinize concepts such as elevation beamforming and Full Dimension-Multiple Input Multiple Output. However, existing studies have mainly been carried out with commercial tools, thus largely limiting their reproducibility. This paper provides a guideline for the practical implementation of the 3D channel model into existing link-and system level simulation tools. Considering the complexity of the model itself, our main focus is on computational efficiency. We validate our approach with the Vienna LTE-A Downlink System Level Simulator and present simulation examples with various planar antenna arrays and polarization schemes.
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