674 research outputs found
Low-complexity Location-aware Multi-user Massive MIMO Beamforming for High Speed Train Communications
Massive Multiple-input Multiple-output (MIMO) adaption is one of the primary
evolving objectives for the next generation high speed train (HST)
communication system. In this paper, we consider how to design an efficient
low-complexity location-aware beamforming for the multi-user (MU) massive MIMO
system in HST scenario. We first put forward a low-complexity beamforming based
on location information, where multiple users are considered. Then, without
considering inter-beam interference, a closed-form solution to maximize the
total service competence of base station (BS) is proposed in this MU HST
scenario. Finally, we present a location-aid searching-based suboptimal
solution to eliminate the inter-beam interference and maximize the BS service
competence. Various simulations are given to exhibit the advantages of our
proposed massive MIMO beamforming method.Comment: This paper has been accepted for future publication by VTC2017-Sprin
A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends
This paper examines the security vulnerabilities and threats imposed by the
inherent open nature of wireless communications and to devise efficient defense
mechanisms for improving the wireless network security. We first summarize the
security requirements of wireless networks, including their authenticity,
confidentiality, integrity and availability issues. Next, a comprehensive
overview of security attacks encountered in wireless networks is presented in
view of the network protocol architecture, where the potential security threats
are discussed at each protocol layer. We also provide a survey of the existing
security protocols and algorithms that are adopted in the existing wireless
network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term
evolution (LTE) systems. Then, we discuss the state-of-the-art in
physical-layer security, which is an emerging technique of securing the open
communications environment against eavesdropping attacks at the physical layer.
We also introduce the family of various jamming attacks and their
counter-measures, including the constant jammer, intermittent jammer, reactive
jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the
integration of physical-layer security into existing authentication and
cryptography mechanisms for further securing wireless networks. Finally, some
technical challenges which remain unresolved at the time of writing are
summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201
Interference Alignment — Practical Challenges and Test-bed Implementation
Data traffic over wireless communication networks has experienced a
tremendous growth in the last decade, and it is predicted to exponentially
increase in the next decades. Enabling future wireless networks to fulfill this
expectation is a challenging task both due to the scarcity of radio resources
(e.g. spectrum and energy), and also the inherent characteristics of the
wireless transmission medium. Wireless transmission is in general subject to
two phenomena: fading and interference. The elegant interference alignment
concept reveals that with proper transmission signalling design, different
interference signals can in fact be aligned together, such that more radio
resources can be assigned to the desired transmission. Although interference
alignment can achieve a larger data rate compared to orthogonal transmission
strategies, several challenges should be addressed to enable the deployment of
this technique in future wireless networks For instance, to perform
interference alignment, normally, global channel state information (CSI) is
required to be perfectly known at all terminals. Clearly, acquiring such
channel knowledge is a challenging problem in practice and proper channel
training and channel state feedback techniques need to be deployed. In
addition, since the channels are time-varying proper adaptive transmission is
needed. This chapter review recent advances in practical aspects of
interference alignment. It also presents recent test-bed implementations of
signal processing algorithms for the realization of interference alignment.Comment: Book Chapter accepted for publication in the book entitled:
Contemporary Issues in Wireless Communications, ISBN: 978-953-51-4101-3,
Khatib, M. (Ed.), to be published by INTECH Publishers. Expected month of
publication: November 201
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