4,507 research outputs found
Accuracy-Complexity Tradeoff Analysis and Complexity Reduction Methods for Non-Stationary IMT-A MIMO Channel Models
open access journalHigh-mobility wireless communication systems have attracted growing interests in recent years. For the deployment of these systems, one fundamental work is to build accurate and efficient
channel models. In high-mobility scenarios, it has been shown that the standardized channel models, e.g., IMT-Advanced (IMT-A) multiple-input multiple-output (MIMO) channel model, provide noticeable longer
stationary intervals than measured results and the wide-sense stationary (WSS) assumption may be violated.
Thus, the non-stationarity should be introduced to the IMT-A MIMO channel model to mimic the channel characteristics more accurately without losing too much efficiency. In this paper, we analyze and compare
the computational complexity of the original WSS and non-stationary IMT-A MIMO channel models. Both the number of real operations and simulation time are used as complexity metrics. Since introducing the nonstationarity to the IMT-A MIMO channel model causes extra computational complexity, some computation reduction methods are proposed to simplify the non-stationary IMT-A MIMO channel model while retaining an acceptable accuracy. Statistical properties including the temporal autocorrelation function, spatial cross-correlation function, and stationary interval are chosen as the accuracy metrics for verifications. It is shown that the tradeoff between the computational complexity and modeling accuracy can be achieved by using these proposed complexity reduction methods
Separation Framework: An Enabler for Cooperative and D2D Communication for Future 5G Networks
Soaring capacity and coverage demands dictate that future cellular networks
need to soon migrate towards ultra-dense networks. However, network
densification comes with a host of challenges that include compromised energy
efficiency, complex interference management, cumbersome mobility management,
burdensome signaling overheads and higher backhaul costs. Interestingly, most
of the problems, that beleaguer network densification, stem from legacy
networks' one common feature i.e., tight coupling between the control and data
planes regardless of their degree of heterogeneity and cell density.
Consequently, in wake of 5G, control and data planes separation architecture
(SARC) has recently been conceived as a promising paradigm that has potential
to address most of aforementioned challenges. In this article, we review
various proposals that have been presented in literature so far to enable SARC.
More specifically, we analyze how and to what degree various SARC proposals
address the four main challenges in network densification namely: energy
efficiency, system level capacity maximization, interference management and
mobility management. We then focus on two salient features of future cellular
networks that have not yet been adapted in legacy networks at wide scale and
thus remain a hallmark of 5G, i.e., coordinated multipoint (CoMP), and
device-to-device (D2D) communications. After providing necessary background on
CoMP and D2D, we analyze how SARC can particularly act as a major enabler for
CoMP and D2D in context of 5G. This article thus serves as both a tutorial as
well as an up to date survey on SARC, CoMP and D2D. Most importantly, the
article provides an extensive outlook of challenges and opportunities that lie
at the crossroads of these three mutually entangled emerging technologies.Comment: 28 pages, 11 figures, IEEE Communications Surveys & Tutorials 201
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
Advanced Radio Resource Management for Multi Antenna Packet Radio Systems
In this paper, we propose fairness-oriented packet scheduling (PS) schemes
with power-efficient control mechanism for future packet radio systems. In
general, the radio resource management functionality plays an important role in
new OFDMA based networks. The control of the network resource division among
the users is performed by packet scheduling functionality based on maximizing
cell coverage and capacity satisfying, and certain quality of service
requirements. Moreover, multiantenna transmit-receive schemes provide
additional flexibility to packet scheduler functionality. In order to mitigate
inter-cell and co-channel interference problems in OFDMA cellular networks soft
frequency reuse with different power masks patterns is used. Stemming from the
earlier enhanced proportional fair scheduler studies for single-input
multiple-output (SIMO) and multiple-input multipleoutput (MIMO) systems, we
extend the development of efficient packet scheduling algorithms by adding
transmit power considerations in the overall priority metrics calculations and
scheduling decisions. Furthermore, we evaluate the proposed scheduling schemes
by simulating practical orthogonal frequency division multiple access (OFDMA)
based packet radio system in terms of throughput, coverage and fairness
distribution among users. As a concrete example, under reduced overall transmit
power constraint and unequal power distribution for different sub-bands, we
demonstrate that by using the proposed power-aware multi-user scheduling
schemes, significant coverage and fairness improvements in the order of 70% and
20%, respectively, can be obtained, at the expense of average throughput loss
of only 15%.Comment: 14 Pages, IJWM
Preliminary Results on 3D Channel Modeling: From Theory to Standardization
Three dimensional beamforming (3D) (also elevation beamforming) is now
gaining a growing interest among researchers in wireless communication. The
reason can be attributed to its potential to enable a variety of strategies
like sector or user specific elevation beamforming and cell-splitting. Since
these techniques cannot be directly supported by current LTE releases, the 3GPP
is now working on defining the required technical specifications. In
particular, a large effort is currently made to get accurate 3D channel models
that support the elevation dimension. This step is necessary as it will
evaluate the potential of 3D and FD(Full Dimensional) beamforming techniques to
benefit from the richness of real channels. This work aims at presenting the
on-going 3GPP study item "Study on 3D-channel model for Elevation Beamforming
and FD-MIMO studies for LTE", and positioning it with respect to previous
standardization works
Context-aware Cluster Based Device-to-Device Communication to Serve Machine Type Communications
Billions of Machine Type Communication (MTC) devices are foreseen to be
deployed in next ten years and therefore potentially open a new market for next
generation wireless network. However, MTC applications have different
characteristics and requirements compared with the services provided by legacy
cellular networks. For instance, an MTC device sporadically requires to
transmit a small data packet containing information generated by sensors. At
the same time, due to the massive deployment of MTC devices, it is inefficient
to charge their batteries manually and thus a long battery life is required for
MTC devices. In this sense, legacy networks designed to serve human-driven
traffics in real time can not support MTC efficiently. In order to improve the
availability and battery life of MTC devices, context-aware device-to-device
(D2D) communication is exploited in this paper. By applying D2D communication,
some MTC users can serve as relays for other MTC users who experience bad
channel conditions. Moreover, signaling schemes are also designed to enable the
collection of context information and support the proposed D2D communication
scheme. Last but not least, a system level simulator is implemented to evaluate
the system performance of the proposed technologies and a large performance
gain is shown by the numerical results
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