6,016 research outputs found
Wide Band Propagation in Train-to-Train Scenarios - Measurement Campaign and First Results
Within the next decades the railway systems will change to fully autonomous high speed trains (HSTs). An increase in efficiency and safety and a reduction of costs would go hand in hand. Today’s centralized railway management system and established regulations can not cope with trains driving within the absolute braking distance as it would be necessary for electronic coupling or platooning maneuvers. Hence, to ensure safety and reliability, new applications and changes in the train control and management are necessary. Such changes demand new reliable control communication links between train-to-train (T2T) and future developments on train-to-ground (T2G). T2G will be covered by long term evolution-railway (LTE-R) which shall replace today’s global system for mobile communications-railway (GSM-R). The decentralized T2T communication is hardly investigated and no technology has been selected. This publication focuses on the wide band propagation for T2T scenarios and describes a extensive channel sounding measurement campaign with two HSTs. First results of T2T communication at high speed
conditions in different environments are presented
Improved Handover Through Dual Connectivity in 5G mmWave Mobile Networks
The millimeter wave (mmWave) bands offer the possibility of orders of
magnitude greater throughput for fifth generation (5G) cellular systems.
However, since mmWave signals are highly susceptible to blockage, channel
quality on any one mmWave link can be extremely intermittent. This paper
implements a novel dual connectivity protocol that enables mobile user
equipment (UE) devices to maintain physical layer connections to 4G and 5G
cells simultaneously. A novel uplink control signaling system combined with a
local coordinator enables rapid path switching in the event of failures on any
one link. This paper provides the first comprehensive end-to-end evaluation of
handover mechanisms in mmWave cellular systems. The simulation framework
includes detailed measurement-based channel models to realistically capture
spatial dynamics of blocking events, as well as the full details of MAC, RLC
and transport protocols. Compared to conventional handover mechanisms, the
study reveals significant benefits of the proposed method under several
metrics.Comment: 16 pages, 13 figures, to appear on the 2017 IEEE JSAC Special Issue
on Millimeter Wave Communications for Future Mobile Network
In-vehicle channel sounding in the 5.8-GHz band
The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard. Experiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential decay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating in the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and characterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample Kolmogorov-Smirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves better for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p simulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly vouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments.The article reports vehicular channel measurements in the frequency band of 5.8 GHz for IEEE 802.11p standard. Experiments for both intra-vehicle and out-of-vehicle environments were carried out. It was observed that the large-scale variations (LSVs) of the power delay profiles (PDPs) can be best described through a two-term exponential decay model, in contrast to the linear models which are suitable for popular ultra-wideband (UWB) systems operating in the 3- to 11-GHz band. The small-scale variations (SSVs) are separated from the PDP by subtracting the LSV and characterized utilizing logistic, generalized extreme value (GEV), and normal distributions. Two sample Kolmogorov-Smirnov (K-S) tests validated that the logistic distribution is optimal for in-car, whereas the GEV distribution serves better for out-of-car measurements. For each measurement, the LSV trend was used to construct the respective channel impulse response (CIR), i.e., tap gains at different delays. Next, the CIR information is fed to an 802.11p simulation testbed to evaluate the bit error rate (BER) performance, following a Rician model. The BER results strongly vouch for the suitability of the protocol for in-car as well as out-of-car wireless applications in stationary environments
Millimeter Wave Channel Measurements in a Railway Depot
Millimeter wave (mmWave) communication is a key enabling technology with the
potential to deliver high capacity, high peak data rate communications for
future railway services. Knowledge of the radio characteristics is of paramount
importance for the successful deployment of such systems. In this paper mmWave
channel measurements are reported for a railway environment using a wideband
channel sounder operating at 60GHz. Highly directional antennas are deployed at
both ends of the link. Data is reported for path loss, root mean square (RMS)
delay spread and K-factor. Static and mobile measurements are considered.
Analysis shows that the signal strength is strongly dependent (up to 25dB) on
the azimuth orientation of the directional transmit and receive antennas. A
path loss exponent of n=2.04 was extracted from the Line-of-Sight measurements
with optimally aligned antennas. RMS delay spreads ranged from 1ns to 22ns
depending on antenna alignment. 50% of the measured K-factors were found to be
less than 6dB. We conclude this is the result of ground reflections in the
vertical Tx-Rx plane
An Efficient Uplink Multi-Connectivity Scheme for 5G mmWave Control Plane Applications
The millimeter wave (mmWave) frequencies offer the potential of orders of
magnitude increases in capacity for next-generation cellular systems. However,
links in mmWave networks are susceptible to blockage and may suffer from rapid
variations in quality. Connectivity to multiple cells - at mmWave and/or
traditional frequencies - is considered essential for robust communication. One
of the challenges in supporting multi-connectivity in mmWaves is the
requirement for the network to track the direction of each link in addition to
its power and timing. To address this challenge, we implement a novel uplink
measurement system that, with the joint help of a local coordinator operating
in the legacy band, guarantees continuous monitoring of the channel propagation
conditions and allows for the design of efficient control plane applications,
including handover, beam tracking and initial access. We show that an
uplink-based multi-connectivity approach enables less consuming, better
performing, faster and more stable cell selection and scheduling decisions with
respect to a traditional downlink-based standalone scheme. Moreover, we argue
that the presented framework guarantees (i) efficient tracking of the user in
the presence of the channel dynamics expected at mmWaves, and (ii) fast
reaction to situations in which the primary propagation path is blocked or not
available.Comment: Submitted for publication in IEEE Transactions on Wireless
Communications (TWC
Broadband radio communications in subway stations and tunnels
Broadband radio communication systems are very important for railway traffic control systems and passengers network services. Nowadays, even though 4G LTE (Long Term Evolution) has deployed for commercial use with excellent results in open areas, it is still lack of knowledge regarding to how such broadband signals propagate inside complex environments with many complex structures that affect propagation such as subway tunnels and stations. For this reason, the aim of the presented measurements in this paper is to model the response of the broadband channel at 1000 MHz and 2450 MHz in the subway environments. These measurements focus on three types of scenarios: subway stations, straight tunnels and a train effect the signal. The results provide detailed information about the propagation channel, which can be useful to develop a broadband propagation model for underground communication systems
6G Enabled Advanced Transportation Systems
The 6th generation (6G) wireless communication network is envisaged to be
able to change our lives drastically, including transportation. In this paper,
two ways of interactions between 6G communication networks and transportation
are introduced. With the new usage scenarios and capabilities 6G is going to
support, passengers on all sorts of transportation systems will be able to get
data more easily, even in the most remote areas on the planet. The quality of
communication will also be improved significantly, thanks to the advanced
capabilities of 6G. On top of providing seamless and ubiquitous connectivity to
all forms of transportation, 6G will also transform the transportation systems
to make them more intelligent, more efficient, and safer. Based on the latest
research and standardization progresses, technical analysis on how 6G can
empower advanced transportation systems are provided, as well as challenges and
insights for a possible road ahead.Comment: Submitted to an open access journa
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