2,409 research outputs found
Realistic geometry-based stochastic channel models for advanced wireless MIMO systems
The employment of multiple antennas at both the Transmitter (Tx) and Receiver (Rx)
enables the so-called Multiple-Input Multiple-Output (MIMO) technologies to greatly
improve the link reliability and increase the overall system capacity. MIMO has been
recommended to be employed in various advanced wireless communication systems,
e.g., the Fourth Generation (4G) wireless systems and beyond. For the successful
design, performance test, and simulation of MIMO wireless communication systems, a
thorough understanding of the underlying MIMO channels and corresponding models
are indispensable. The approach of geometry-based stochastic modelling has widely
been used due to its advantages, such as convenience for theoretical analysis and
mathematical tractability.
In addition, wireless Vehicle-to-Vehicle (V2V) communications play an important role
in mobile relay-based cellular networks, vehicular ad hoc networks, and intelligent
transportation systems. In V2V communication systems, both the Tx and Rx are
in motion and equipped with low elevation antennas. This is di erent from conventional
Fixed-to-Mobile (F2M) cellular systems, where only one terminal moves. This
PhD project is therefore devoted to the modelling and simulation of wireless MIMO
channels for both V2V and F2M communication systems.
In this thesis, we rst propose a novel narrowband Three Dimensional (3D) theoretical
Regular-Shape Geometry Based Stochastic Model (RS-GBSM) and the corresponding
Sum-of-Sinusoids (SoS) simulation model for non-isotropic MIMO V2V Ricean fading
channels. The proposed RS-GBSM has the ability to study the impact of the Vehicular
Tra c Density (VTD) on channel statistics and jointly considers the azimuth
and elevation angles by using the von Mises-Fisher (VMF) distribution. Moreover, a
novel parameter computation method is proposed for jointly calculating the azimuth
and elevation angles in the SoS channel simulator. Based on the proposed 3D theoretical
RS-GBSM and its SoS simulation model, statistical properties are derived
and thoroughly investigated. The impact of the elevation angle in the 3D model on
key statistical properties is investigated by comparing with those of the corresponding
Two Dimensional (2D) model. It is demonstrated that the 3D model is more practical
to characterise real V2V channels, in particular for pico-cell scenarios.
Secondly, actual V2V channel measurements have shown that the modelling assumption
of Wide Sense Stationary (WSS) is valid only for very short time intervals. This fact inspires the requirement of non-WSS V2V channel models. Therefore, we propose
a novel 3D theoretical wideband MIMO non-WSS V2V RS-GBSM and corresponding
SoS simulation model. Due to the dynamic movement of both the Tx and Rx,
the Angle of Departure (AoD) and Angle of Arrival (AoA) are time-variant, which
makes our model non-stationary. The proposed RS-GBSMs are su ciently generic
and adaptable to mimic various V2V scenarios. Furthermore, important local channel
statistical properties are derived and thoroughly investigated. The impact of
non-stationarity on these channel statistical properties is investigated by comparing
with those of the corresponding WSS model. The proposed non-WSS RS-GBSMs are
validated by measurements in terms of the channel stationary time.
Thirdly, realistic MIMO channel models with a proper trade-o between accuracy
and complexity are indispensable for the practical application. By comparing the
accuracy and complexity of two latest F2M standardised channel models (i.e., LTE-A
and IMT-A channel models), we employ some channel statistical properties as the
accuracy metrics and the number of Real Operations (ROs) as the complexity metric.
It is shown that the LTE-A MIMO channel model is simple but has signi cant
aws
in terms of the accuracy. The IMT-A channel model is complicated but has better
accuracy. Therefore, we focus on investigating various complexity reduction methods
to simplify the IMT-A channel model. The results have shown that the proposed
methods do not degrade much the accuracy of the IMT-A channel model, whereas
they can signi cantly reduce the complexity in terms of the number of ROs and
channel coe cients computing time.
Finally, to investigate the non-stationarity of the IMT-A MIMO channel model, we
further propose a non-WSS channel model with time-varying AoDs and AoAs. The
proposed time-varying functions can be applied to various scenarios according to moving
features of Moving Clusters (MCs) and a Mobile Station (MS). Moreover, the impacts
of time-varying AoDs and AoAs on local statistical properties are investigated
thoroughly. Simulation results prove that statistical properties are varied with time
due to the non-stationarity of the proposed channel model.
In summary, the proposed reference models and channel simulators are useful for
the design, testing, and performance evaluation of advanced wireless V2V and F2M
MIMO communication systems
A 3D Non-Stationary MIMO Channel Model for Reconfigurable Intelligent Surface Auxiliary UAV-To-Ground MmWave Communications
Unmanned aerial vehicle (UAV) communications exploiting millimeter wave (mmWave) can satisfy the increasing data rate demands for future wireless networks owing to the line-of-sight (LoS) dominated transmission and flexibility. In reality, the LoS link can be easily and severely blocked due to poor propagation environments such as tall buildings or trees. To this end, we introduce a reconfigurable intelligent surface (RIS), which passively reflects signals with programmable reflection coefficients, between the transceivers to enhance the communication quality. Specifically, in this paper we generalize a three-dimensional (3D) non-stationary wideband end-to-end channel model for RIS auxiliary UAV-to-ground mmWave multiple-input multiple-output (MIMO) communication systems. By modeling the RIS as a virtual cluster, we study the power delivering capability of RIS as well as the fading characteristic of the proposed channel model. Important channel statistical properties are derived and thoroughly investigated, and the impact of RIS reflection phase configurations on these statistical properties is studied, which provides guidelines for the practical system design. The agreement between theoretical and simulated as well as measurement results validate the effectiveness of the proposed channel model
A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles
In recent years, there has been a dramatic increase in the use of unmanned
aerial vehicles (UAVs), particularly for small UAVs, due to their affordable
prices, ease of availability, and ease of operability. Existing and future
applications of UAVs include remote surveillance and monitoring, relief
operations, package delivery, and communication backhaul infrastructure.
Additionally, UAVs are envisioned as an important component of 5G wireless
technology and beyond. The unique application scenarios for UAVs necessitate
accurate air-to-ground (AG) propagation channel models for designing and
evaluating UAV communication links for control/non-payload as well as payload
data transmissions. These AG propagation models have not been investigated in
detail when compared to terrestrial propagation models. In this paper, a
comprehensive survey is provided on available AG channel measurement campaigns,
large and small scale fading channel models, their limitations, and future
research directions for UAV communication scenarios
Stationarity analysis of V2I radio channel in a suburban environment
Due to rapid changes in the environment, vehicular communication channels no longer satisfy the assumption of wide-sense stationary uncorrelated scattering. The non-stationary fading process can be characterized by assuming local stationarity regionswith finite extent in time and frequency. The local scattering function (LSF) and channel correlation function (CCF) provide a framework to characterize the mean power and correlation of the non-stationary channel scatterers, respectively. In this paper, we estimate the LSF and CCF from measurements collected in a vehicle-to-infrastructure radio channel sounding campaign in a suburban environment in Lille, France. Based on the CCF, the stationarity region is evaluated in time as 567 ms and used to capture the non-stationary fading parameters. We obtain the time-varying delay and Doppler power profiles fromthe LSF, and we analyze the corresponding root-mean-square delay and Doppler spreads. We show that the distribution of these parameters follows a lognormal model. Finally, application relevance in terms of channel capacity and diversity techniques is discussed. Results show that the assumption of ergodic capacity and the performance of various diversity techniques depend on the stationarity and coherence parameters of the channel. The evaluation and statistical modeling of such parameters can provide away of tracking channel variation, hence, increasing the performance of adaptive schemes
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