737 research outputs found
MIMO channel modelling and simulation for cellular and mobile-to-mobile
Recently, mobile-to-mobile (M2M) communications have received much attention due
to several emerging applications, such as wireless mobile ad hoc networks, relay-based
cellular networks, and dedicated short range communications (DSRC) for intelligent
transportation systems (e.g., IEEE 802.11p standard). Different from conventional
fixed-to-mobile (F2M) cellular systems, in M2M systems both the transmitter (Tx)
and receiver (Rx) are in motion and often equipped with low elevation antennas.
Multiple-input-multiple-output (MIMO) technologies, employing multiple antennas
at both the Tx and Rx, have widely been adopted for the third generation (3G) and
beyond-3G (B3G) F2M cellular systems due to their potential benefits of improving
coverage, link reliability, and overall system capacity. More recently, MIMO has been
receiving more and more attention for M2M systems as well.
Reliable knowledge of the propagation channel obtained from channel measurements
and corresponding channel models serve as the enabling foundation for the design
and analysis of MIMO F2M and M2M systems. Furthermore, the development of
accurate MIMO F2M and M2M channel simulation models plays a major role in the
practical simulation and performance evaluation of these systems. These form the
primary motivation behind our research on MIMO channel modelling and simulation
for F2M cellular and M2M communication systems.
In this thesis, we first propose a new wideband theoretical multiple-ring based MIMO
regular-shaped geometry-based stochastic model (RS-GBSM) for non-isotropic scattering
F2M macro-cell scenarios and then derive a generic space-time-frequency (STF)
correlation function (CF). The proposed theoretical reference wideband model can be
reduced to a narrowband one-ring model, a new closed-form STF CF of which is derived
as well. Narrowband and wideband sum-of-sinusoids (SoS) simulation models
are then developed, demonstrating a good agreement with the corresponding reference
models in terms of correlation functions.
Secondly, based on a well-known narrowband two-ring single-input single-output (SISO)
M2M channel reference model, we propose new deterministic and stochastic SoS simulation
models for non-isotropic scattering environments. The proposed deterministic
simulator is the first SISO M2M deterministic simulator with good performance, while
the proposed stochastic simulator outperforms the existing one in terms of fitting the
desired statistical properties of the corresponding reference model.
Thirdly, a new adaptive narrowband MIMO M2M RS-GBSM is proposed for nonisotropic
scattering environments. To the best of our knowledge, the proposed M2M
model is the first RS-GBSM that has the ability to study the impact of the vehicular
traffic density on channel statistics. From the proposed theoretical reference
model, we comprehensively investigate some important M2M channel statistics including
the STF CF, space-Doppler-frequency power spectral density, envelope level
crossing rate, and average fade duration. A close agreement between some channel
statistics obtained from the proposed reference model and measurement data is
observed, confirming the utility of our model.
Finally, we extend the above narrowband model to a new wideband MIMO M2M RSGBSM
with respect to the frequency-selectivity. The proposed wideband reference
model is validated by observing a good match between some statistical properties of
the theoretical model and available measurement data. From the wideband reference
model, we further design new wideband deterministic and stochastic SoS simulation
models. The proposed wideband simulators can be easily reduced to narrowband
ones. The utilities of the newly derived narrowband and wideband simulation models
are validated by comparing their statistical properties with those of the corresponding
reference models.
The proposed channel reference models and simulators are expected to be useful for
the design, testing, and performance evaluation of future MIMO cellular and M2M
communication systems.Scottish Funding Counci
MIMO Systems: Principles, Iterative Techniques, and advanced Polarization
International audienceThis chapter considers the principles of multiple-input multiple-output (MIMO) wireless communication systems as well as some recent accomplishments concerning their implementation. By employing multiple antennas at both transmitter and receiver, very high data rates can be achieved under the condition of deployment in a rich-scattering propagation medium. This interesting property of MIMO systems suggests their use in the future high-rate and high-quality wireless communication systems. Several concepts in MIMO systems are reviewed in this chapter. We first consider MIMO channel models and recall the basic principles of MIMO structures and channel modeling. We next study the MIMO channel capacity and present the early developments in these systems concerning the information theory aspect. Iterative signal detection is considered next; it considers iterative techniques for space-time decoding. As the capacity is inversely proportional to the spatial channel correlation, MIMO antennas should be sufficiently separated, usually by several wavelengths. In order to minimize antennas' deployment, we present advanced polarization diversity techniques for MIMO systems and explain how they can help to reduce the spatial correlation in order to achieve high transmission rates. We end the chapter by considering the application of MIMO systems in local area networks, as well as their potential in enhancing range, localization, and power efficiency of sensor networks
Full-Duplex Cloud Radio Access Network: Stochastic Design and Analysis
Full-duplex (FD) has emerged as a disruptive communications paradigm for
enhancing the achievable spectral efficiency (SE), thanks to the recent major
breakthroughs in self-interference (SI) mitigation. The FD versus half-duplex
(HD) SE gain, in cellular networks, is however largely limited by the
mutual-interference (MI) between the downlink (DL) and the uplink (UL). A
potential remedy for tackling the MI bottleneck is through cooperative
communications. This paper provides a stochastic design and analysis of FD
enabled cloud radio access network (C-RAN) under the Poisson point process
(PPP)-based abstraction model of multi-antenna radio units (RUs) and user
equipments (UEs). We consider different disjoint and user-centric approaches
towards the formation of finite clusters in the C-RAN. Contrary to most
existing studies, we explicitly take into consideration non-isotropic fading
channel conditions and finite-capacity fronthaul links. Accordingly,
upper-bound expressions for the C-RAN DL and UL SEs, involving the statistics
of all intended and interfering signals, are derived. The performance of the FD
C-RAN is investigated through the proposed theoretical framework and
Monte-Carlo (MC) simulations. The results indicate that significant FD versus
HD C-RAN SE gains can be achieved, particularly in the presence of
sufficient-capacity fronthaul links and advanced interference cancellation
capabilities
Mobile to mobile channel modelling for wireless communications
Wireless communication has been experiencing many recent advances in mobile to mobile (M2M) applications. M2M communication systems differ from conventional fixed to mobile systems by having both transmitter and receiver in low elevation and in motion. This raises the need to come up with new channel models and perform statistical analysis on M2M communication channels looking from a different perspective. This need motivated us to perform the research outlined in this thesis. In reviewing the literature we found that though in general the M2M channel models are sparse, a major gap exists in the non geometrical stochastic based mathematical channel models. In filling this gap, we develop a novel mathematical non geometrical stochastic multiple input multiple output (MIMO) M2M channel model for two dimensional (2D) and three dimensional (3D) scattering environments. This model is based on the underlying physics of free space wave propagation and can be used as a framework for any environment by selecting suitable complex scattering gain functions. In addition, we extend this novel model to multicarrier M2M which is the first multicarrier channel model in the non geometrical stochastic M2M category. Based on our novel M2M channel model, we carry out an extensive analysis in space-time correlation, space-frequency correlation and second order channel statistics. With the choice of suitable parameters, this analysis and channel model can be used for any wireless environment. Thus, we claim that our novel channel model together with the analysis performed in this thesis can be taken as a generalized framework. A significant contribution of our analysis is the consideration of the impact of transmitter and receiver speed to space-time and space-frequency correlation, which is not available in the literature. Using a von Mises-Fisher distribution as the angular power distribution, the usefulness of the derived temporal correlation function is discussed. The simulation results corroborate the fact that both space-time and space-frequency correlations are reduced when transmitter or receiver speed increases. The rate of reduction of space-time correlation in von Mises-Fisher distribution scattering environment is more than in the isotropic environment. Under second order channel statistics, we consider Rice, Rayleigh and Nakagami fading channels in four different non-isotropic scattering environments with angle of departure (AoD) and angle of arrival (AoA) distributions given by (i) separable Truncated Gaussian, (ii) separable von-Mises, (iii) truncated Gaussian bivariate and (iv) truncated Laplacian bivariate distributions. We show that the major second order statistics, namely, the level crossing rate (LCR) and the average fade duration (AFD), in different fading channels can be expressed in terms of known scattering coefficients of the AoD and AoA distributions. As the channel models and their respective measurements provide reliable knowledge of the channel for the design and analysis of M2M systems, the proposed channel model and the corresponding analysis will be useful for the design, testing and performance evaluation of future M2M communication systems
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
Channel Modeling and Characteristics for 6G Wireless Communications
[EN] Channel models are vital for theoretical analysis, performance evaluation, and system deployment of the communication systems between the transmitter and receivers. For sixth-generation (6G) wireless networks, channel modeling and characteristics analysis should combine different technologies and disciplines, such as high-mobil-ity, multiple mobilities, the uncertainty of motion trajectory, and the non-stationary nature of time/frequency/space domains. In this article, we begin with an overview of the salient characteristics in the modeling of 6G wireless channels. Then, we discuss the advancement of channel modeling and characteristics analysis for next-generation communication systems. Finally, we outline the research challenges of channel models and characteristics in 6G wireless communications.This research was supported by the National Key R&D Program of China under grant 2018YFB1801101; the National Nature Science Foundation of China (No. 61771248 and 61971167); the Jiangsu Province Research Scheme of Nature Science for Higher Education Institution (No. 14KJA510001); and the Open Research Fund of the National Mobile Communications Research Laboratory, Southeast University (No. 2020D14).Jiang, H.; Mukherjee, M.; Zhou, J.; Lloret, J. (2021). Channel Modeling and Characteristics for 6G Wireless Communications. IEEE Network. 35(1):296-303. https://doi.org/10.1109/MNET.011.200034829630335
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