118 research outputs found
Secrecy Spectrum and Energy Efficiency Analysis in Massive MIMO-enabled Multi-Tier Hybrid HetNets
Massive multiple antenna systems in conjunction with millimeter (mmWave) communication have gained tremendous attention in the recent years owing to their high speed data delivery. However, security in these networks has been overlooked; thereby necessitating a comprehensive study. This paper analyzes the physical layer security performance of the downlink of a massive multiple-input multiple-output (MIMO)-based hybrid heterogeneous network (HetNet) where both mmWave and sub-6 GHz small cells coexist. Specifically, a tractable approach using stochastic geometry is proposed to analyze the secrecy outage probability, secrecy energy efficiency (SEE) and secrecy spectrum efficiency (SSE) of the hybrid HetNets. Our study further characterizes the impact of large antenna arrays, directional beamforming gains, transmit power, and cell density on the above mentioned secrecy performance measures. The results show that at low transmit power operation, the secrecy performance enhances for higher small cell density. It has also been observed that the higher directivity gains at mmWave cells lead to a drop in secrecy performance of the network; thus a tradeoff exists between better coverage or secrecy
A New Look at Physical Layer Security, Caching, and Wireless Energy Harvesting for Heterogeneous Ultra-dense Networks
Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low
latency through the use of dense sub-6 GHz and millimeter wave (mmWave) small
cells with different antenna configurations. Existing work has widely studied
spectral and energy efficiency in such networks and shown that high spectral
and energy efficiency can be achieved. This article investigates the benefits
of heterogeneous ultra-dense network architecture from the perspectives of
three promising technologies, i.e., physical layer security, caching, and
wireless energy harvesting, and provides enthusiastic outlook towards
application of these technologies in heterogeneous ultra-dense networks. Based
on the rationale of each technology, opportunities and challenges are
identified to advance the research in this emerging network.Comment: Accepted to appear in IEEE Communications Magazin
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
Secrecy and Energy Efficiency in Massive MIMO Aided Heterogeneous C-RAN: A New Look at Interference
In this paper, we investigate the potential benefits of the massive
multiple-input multiple-output (MIMO) enabled heterogeneous cloud radio access
network (C-RAN) in terms of the secrecy and energy efficiency (EE). In this
network, both remote radio heads (RRHs) and massive MIMO macrocell base
stations (BSs) are deployed and soft fractional frequency reuse (S-FFR) is
adopted to mitigate the inter-tier interference. We first examine the physical
layer security by deriving the area ergodic secrecy rate and secrecy outage
probability. Our results reveal that the use of massive MIMO and C-RAN can
greatly improve the secrecy performance. For C-RAN, a large number of RRHs
achieves high area ergodic secrecy rate and low secrecy outage probability, due
to its powerful interference management. We find that for massive MIMO aided
macrocells, having more antennas and serving more users improves secrecy
performance. Then we derive the EE of the heterogeneous C-RAN, illustrating
that increasing the number of RRHs significantly enhances the network EE.
Furthermore, it is indicated that allocating more radio resources to the RRHs
can linearly increase the EE of RRH tier and improve the network EE without
affecting the EE of the macrocells.Comment: 26 pages, 11 figures, to appear in IEEE Journal of Selected Topics in
Signal Processin
Security for 5G Mobile Wireless Networks
The advanced features of 5G mobile wireless network systems yield new security requirements and challenges. This paper presents a comprehensive survey on security of 5G wireless network systems compared to the traditional cellular networks. The paper starts with a review on 5G wireless networks particularities as well as on the new requirements and motivations of 5G wireless security. The potential attacks and security services with the consideration of new service requirements and new use cases in 5G wireless networks are then summarized. The recent development and the existing schemes for the 5G wireless security are presented based on the corresponding security services including authentication, availability, data confidentiality, key management and privacy. The paper further discusses the new security features involving different technologies applied to 5G such as heterogeneous networks, device-to-device communications, massive multiple-input multiple-output, software defined networks and Internet of Things. Motivated by these security research and development activities, we propose a new 5G wireless security architecture, based on which the analysis of identity management and flexible authentication is provided. As a case study, we explore a handover procedure as well as a signaling load scheme to show the advantage of the proposed security architecture. The challenges and future directions of 5G wireless security are finally summarized
A new look at physical layer security, caching, and wireless energy harvesting for heterogeneous ultra-dense networks
Heterogeneous ultra-dense networks enable ultra-high data rates and ultra-low latency through the use of dense sub-6 GHz and millimeter-wave small cells with different antenna configurations. Existing work has widely studied spectral and energy efficiency in such networks and shown that high spectral and energy efficiency can be achieved. This article investigates the benefits of heterogeneous ultra-dense network architecture from the perspectives of three promising technologies, physical layer security, caching, and wireless energy harvesting, and provides an enthusiastic outlook toward application of these technologies in heterogeneous ultra-dense networks. Based on the rationale of each technology, opportunities and challenges are identified to advance the research in this emerging network
Efficient resource allocation for 5G hybrid wireless networks
This thesis explores three directions of energy-efficiency(EE) and spectral efficiency(SE) under 5G wireless networks. Firstly, we study the optimization of power control for the small (two-user) interference channel in which the terminals are time-switched between the signal-processing and energy-harvesting phases. Both energy harvesting and signal-processing processes are during the downlink. The objective is to maximize the sum-rate, subject to the minimum data and harvested energy constraints at the receivers, assuming a fixed time-switching coefficient. The key contribution is using a geometric approach that analyzes the feasible region governed by the constraints, which gives rise to the optimal power control solution. Another topic focuses on the performance analysis of two user association schemes for wireless power transfer (WPT) in heterogeneous networks (HetNets) massive multiple-input multiple-output (MIMO) antennas, downlink for the WPT in the first phase and uplink for wireless information transfer (WIT) in the second phase. The two user association schemes considered in the analysis are the Downlink received signal power (DRSP) based approach for maximizing the harvested energy; and the uplink received signal power (URSP) based approach for minimizing the uplink path loss. In the downlink, we adopt a low-complexity approach for massive MIMO power transfer to recharge users. Then we derive the average uplink achievable rate with the harvested energy. The last topic analyses a large-scale mmWave ad hoc network in the randomly located eavesdroppers area, where eavesdroppers can still intercept the confidential messages, since they may reside in the signal beam. This chapter explores the potential of physical layer security in mmWave ad hoc networks. Specifically, we characterize the impact of mmWave channel characteristics, random blockages, and antenna gains on the secrecy performance. For the special case of the uniform linear array (ULA), a tractable approach is proposed to evaluate the average achievable secrecy rate
Non-Orthogonal Multiple Access for 5G: Design and Performance Enhancement
PhDSpectrum scarcity is one of the most important challenges in wireless communications
networks due to the sky-rocketing growth of multimedia applications. As the latest
member of the multiple access family, non-orthogonal multiple access (NOMA) has
been recently proposed for 3GPP Long Term Evolution (LTE) and envisioned to be
a key component of the 5th generation (5G) mobile networks for its potential ability on
spectrum enhancement. The feature of NOMA is to serve multiple users at the same
time/frequency/code, but with di erent power levels, which yields a signi cant spectral
e ciency gain over conventional orthogonal multiple access (OMA). This thesis provides
a systematic treatment of this newly emerging technology, from the basic principles of
NOMA, to its combination with simultaneously information and wireless power transfer
(SWIPT) technology, to apply in cognitive radio (CR) networks and Heterogeneous
networks (HetNets), as well as enhancing the physical layer security and addressing the
fairness issue.
First, this thesis examines the application of SWIPT to NOMA networks with spatially
randomly located users. A new cooperative SWIPT NOMA protocol is proposed, in
which near NOMA users that are close to the source act as energy harvesting relays in
the aid of far NOMA users. Three user selection schemes are proposed to investigate
the e ect of locations on the performance. Besides the closed-form expressions in terms
of outage probability and throughput, the diversity gain of the considered networks is
determined.
Second, when considering NOMA in CR networks, stochastic geometry tools are used to
evaluate the outage performance of the considered network. New closed-form expressions
are derived for the outage probability. Diversity order of NOMA users has been analyzed
based on the derived outage probability, which reveals important design insights regarding the interplay between two power constraints scenarios.
Third, a new promising transmission framework is proposed, in which massive multipleinput
multiple-output (MIMO) is employed in macro cells and NOMA is adopted in
small cells. For maximizing the biased average received power at mobile users, a massive
MIMO and NOMA based user association scheme is developed. Analytical expressions
for the spectrum e ciency of each tier are derived using stochastic geometry. It is
con rmed that NOMA is capable of enhancing the spectrum e ciency of the network
compared to the OMA based HetNets.
Fourth, this thesis investigates the physical layer security of NOMA in large-scale networks
with invoking stochastic geometry. Both single-antenna and multiple-antenna
aided transmission scenarios are considered, where the base station (BS) communicates
with randomly distributed NOMA users. In addition to the derived exact analytical
expressions for each scenario, some important insights such as secrecy diversity order
and large antenna array property are obtained by carrying the asymptotic analysis.
Fifth and last, the fundamental issues of fairness surrounding the joint power allocation
and dynamic user clustering are addressed in MIMO-NOMA systems in this thesis. A
two-step optimization approach is proposed to solve the formulated problem. Three
e cient suboptimal algorithms are proposed to reduce the computational complexity.
To further improve the performance of the worst user in each cluster, power allocation
coe cients are optimized by using bi-section search. Important insights are concluded
from the generated simulate results
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