2,417 research outputs found
ns-3 Implementation of the 3GPP MIMO Channel Model for Frequency Spectrum above 6 GHz
Communications at mmWave frequencies will be a key enabler of the next
generation of cellular networks, due to the multi-Gbps rate that can be
achieved. However, there are still several problems that must be solved before
this technology can be widely adopted, primarily associated with the interplay
between the variability of mmWave links and the complexity of mobile networks.
An end-to-end network simulator represents a great tool to assess the
performance of any proposed solution to meet the stringent 5G requirements.
Given the criticality of channel propagation characteristics at higher
frequencies, we present our implementation of the 3GPP channel model for the
6-100 GHz band for the ns-3 end-to-end 5G mmWave module, and detail its
associated MIMO beamforming architecture
Evaluation of performance of mobile terminal antennas
Fast development of new mobile communications equipment results in demand for fast and reliable evaluation methods to estimate the performance of mobile terminals because the performance of antennas located on the terminals varies in different multipath propagation environments. Two methods presented in this thesis provide new possibilities in antenna design because, from now on, the performance of new antennas can be tested already before a prototype antenna is constructed by using existing radio channel libraries and simulated radiation patterns of the antennas. The performance can be estimated by calculating the mean effective gain (MEG) of the antenna using the elevation power distribution or by a plane wave -based method using sets of incident plane waves and the radiation pattern of an antenna. In addition to different propagation environments, the effects of the user on performance can be included in the evaluation.
In this thesis, estimating the MEG of different antennas using the elevation power distribution and the power patterns of the antennas is shown to be an accurate and fast method by comparing the results with direct radio channel measurements. The mean difference between the methods is â0.18Â dB with standard deviation of 0.19Â dB. The usefulness of the evaluation method is demonstrated by evaluating the performance of several antennas located on mobile terminals. The antenna evaluation provided important and unique knowledge of the effect of both the environment and the user on performance. Because in calculating the radiation efficiency of the antenna we assume uniform incident field, the efficiency can result in a performance estimation that does not correspond to real usage situations. Therefore, including the environmental effects in the evaluation procedure is important, although the effect of the antenna is more important than the effect of the environment on MEG. It was noticed with calculated Gaussian-shaped beams that tilting or changing the beamwidth of a mobile terminal antenna has an effect of about 2Â dB on MEG in multipath environments. Matching the polarization of the antenna to that of the environment can improve the performance more.
A novel incident plane wave -based tool has been developed for evaluating the performance of antenna configurations designed for diversity and Multiple-Input Multiple-Output (MIMO) systems. In this thesis, the instantaneous joint contribution of incident field consisting of a number of extracted plane waves and the complex three-dimensional radiation pattern of the antenna is shown to be accurate and extremely fast way to estimate the diversity advantages of different antenna configurations in time-variable radio channels. The difference between the diversity gains achieved by the plane wave -based method and by the direct radio channel measurements is on average less than 0.9Â dB. Moreover, the radio channel can be exactly the same for all antenna configurations under test.
Furthermore, this thesis includes evaluation of the performance of different MIMO antenna configurations. The studied antenna configurations have been selected from the 16Ă64 MIMO channel measurement data. A novel way of using one omnidirectional reference antenna in a normalization procedure is shown to be reasonable especially in cases of antenna arrays consisting of directive elements. Three different propagation environments are used as evaluation platforms. The azimuth orientation of mobile terminal antennas may influence the performance of a MIMO antenna configuration significantly. In MIMO configurations compact dual-polarized receiving antennas provide capacity performance almost equal to the arrays employing single polarization.reviewe
An Overview of Massive MIMO Research at the University of Bristol
Massive MIMO has rapidly gained popularity as a technology crucial to the
capacity advances required for 5G wireless systems. Since its theoretical
conception six years ago, research activity has grown exponentially, and there
is now a developing industrial interest to commercialise the technology. For
this to happen effectively, we believe it is crucial that further pragmatic
research is conducted with a view to establish how reality differs from
theoretical ideals. This paper presents an overview of the massive MIMO
research activities occurring within the Communication Systems & Networks Group
at the University of Bristol centred around our 128-antenna real-time testbed,
which has been developed through the BIO programmable city initiative in
collaboration with NI and Lund University. Through recent preliminary trials,
we achieved a world first spectral efficiency of 79.4 bits/s/Hz, and
subsequently demonstrated that this could be increased to 145.6 bits/s/Hz. We
provide a summary of this work here along with some of our ongoing research
directions such as large-scale array wave-front analysis, optimised power
control and localisation techniques.Comment: Presented at the IET Radio Propagation and Technologies for 5G
Conference (2016). 5 page
Massive MIMO Channel Models: A Survey
The exponential traffic growth of wireless communication
networks gives rise to both the insufficient network
capacity and excessive carbon emissions. Massive multiple-input multiple-output (MIMO) can improve the spectrum efficiency
(SE) together with the energy efficiency (EE) and has been
regarded as a promising technique for the next generation
wireless communication networks. Channel model reflects the
propagation characteristics of signals in radio environments and
is very essential for evaluating the performances of wireless communication
systems. The purpose of this paper is to investigate
the state of the art in channel models of massive MIMO. First,
the antenna array configurations are presented and classified,
which directly affect the channel models and system performance.
Then, measurement results are given in order to reflect the
main properties of massive MIMO channels. Based on these
properties, the channel models of massive MIMO are studied
with different antenna array configurations, which can be used
for both theoretical analysis and practical evaluation
Experimental analysis of multidimensional radio channels
In this thesis new systems for radio channel measurements including space and polarization dimensions are developed for studying the radio propagation in wideband mobile communication systems. Multidimensional channel characterization is required for building channel models for new systems capable of exploiting the spatial nature of the channel. It also gives insight into the dominant propagation mechanisms in complex radio environments, where their prediction is difficult, such as urban and indoor environments.
The measurement systems are based on the HUT/IDC wideband radio channel sounder, which was extended to enable real-time multiple output channel measurements at practical mobile speeds at frequencies up to 18Â GHz. Two dual-polarized antenna arrays were constructed for 2Â GHz, having suitable properties for characterizing the 3-D spatial radio channel at both ends of a mobile communication link. These implementations and their performance analysis are presented.
The usefulness of the developed measurement systems is demonstrated by performing channel measurements at 2Â GHz and analyzing the experimental data. Spatial channels of both the mobile and base stations are analyzed, as well as the double-directional channel that fully characterizes the propagation between two antennas. It is shown through sample results that spatial domain channel measurements can be used to gain knowledge on the dominant propagation mechanisms or verify the current assumptions. Also new statistical information about scatterer distribution at the mobile station in urban environment is presented based on extensive real-time measurements. The developed techniques and collected experimental data form a good basis for further comparison with existing deterministic propagation models and development of new spatial channel models.reviewe
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