46 research outputs found
Secure Massive MIMO Transmission with an Active Eavesdropper
In this paper, we investigate secure and reliable transmission strategies for
multi-cell multi-user massive multiple-input multiple-output (MIMO) systems
with a multi-antenna active eavesdropper. We consider a time-division duplex
system where uplink training is required and an active eavesdropper can attack
the training phase to cause pilot contamination at the transmitter. This forces
the precoder used in the subsequent downlink transmission phase to implicitly
beamform towards the eavesdropper, thus increasing its received signal power.
Assuming matched filter precoding and artificial noise (AN) generation at the
transmitter, we derive an asymptotic achievable secrecy rate when the number of
transmit antennas approaches infinity. For the case of a single-antenna active
eavesdropper, we obtain a closed-form expression for the optimal power
allocation policy for the transmit signal and the AN, and find the minimum
transmit power required to ensure reliable secure communication. Furthermore,
we show that the transmit antenna correlation diversity of the intended users
and the eavesdropper can be exploited in order to improve the secrecy rate. In
fact, under certain orthogonality conditions of the channel covariance
matrices, the secrecy rate loss introduced by the eavesdropper can be
completely mitigated.Comment: Accepted by IEEE Transactions on Information Theory. arXiv admin
note: text overlap with arXiv:1505.0123
Jamming Detection in Massive MIMO Systems
This paper considers the physical layer security of a pilot-based massive
multiple-input multiple-output (MaMIMO) system in presence of a multi-antenna
jammer. To improve security of the network, we propose a new jamming detection
method that makes use of a generalized likelihood ratio test over some
coherence blocks. Our proposed method utilizes intentionally unused pilots in
the network. The performance of the proposed detector improves by increasing
the number of antennas at the base station, the number of unused pilots and
also by the number of the coherence blocks that are utilized. Simulation
results confirm our analyses and show that in the MaMIMO regime, perfect
detection (i.e., correct detection probability is one) is achievable even with
a small number of unused pilots.Comment: 5 pages, 2 figures, to appear in IEEE Wireless Communications Letter
On the Fundamental Limits of MIMO Massive Multiple Access Channels
In this paper, we study the multiple-antenna wireless communication networks,
where a large number of devices simultaneously communicate with an access
point. The capacity region of multiple-input multiple-output massive multiple
access channels (MIMO mMAC) is investigated. While joint typicality decoding is
utilized to establish the achievability of capacity region for conventional MAC
with fixed number of users, the technique is not directly applicable for MIMO
mMAC. Instead, an information-theoretic approach based on Gallager's error
exponent analysis is exploited to characterize the
\textcolor[rgb]{0,0,0}{finite dimension region} of MIMO mMAC. Theoretical
results reveal that the finite dimension region of MIMO mMAC is dominated by
sum rate constraint only, and the individual user rate is determined by a
specific factor that corresponds to the allocation of sum rate. The rate in
conventional MAC is not achievable with massive multiple access, which is due
to the fact that successive interference cancellation cannot guarantee an
arbitrary small error decoding probability for MIMO mMAC. The results further
imply that, asymptotically, the individual user rate is independent of the
number of transmit antennas, and channel hardening makes the individual user
rate close to that when only statistic knowledge of channel is available at
receiver. The finite dimension region of MIMO mMAC is a generalization of the
symmetric rate in Chen \emph{et al.} (2017).Comment: Accepted by ICC'201
Joint Millimeter Wave and Microwave Wave Resource Allocation Design for Dual-Mode Base Stations
In this paper, we consider the design of joint resource blocks (RBs) and
power allocation for dual-mode base stations operating over millimeter wave
(mmW) band and microwave (W) band. The resource allocation design aims to
minimize the system energy consumption while taking into account the channel
state information, maximum delay, load, and different types of user
applications (UAs). To facilitate the design, we first propose a group-based
algorithm to assign UAs to multiple groups. Within each group, low-power UAs,
which often appear in short distance and experience less obstacles, are
inclined to be served over mmW band. The allocation problem over mmW band can
be solved by a greedy algorithm. Over W band, we propose an
estimation-optimal-descent algorithm. The rate of each UA at all RBs is
estimated to initialize the allocation. Then, we keep altering RB's ownership
until any altering makes power increases. Simulation results show that our
proposed algorithm offers an excellent tradeoff between low energy consumption
and fair transmission.Comment: Accepted by IEEE WCNC'1
Secrecy Outage of Proactive Relay Selection by Eavesdropper
In this paper, we consider an active eavesdropping scenario in a cooperative
system consisting of a source, a destination, and an active eavesdropper with
multiple decode-and-forward relays. Considering an existing assumption in which
an eavesdropper is also a part of network, a proactive relay selection by the
eavesdropper is proposed. The best relay which maximizes the eavesdropping rate
is selected by the eavesdropper. A relay selection scheme is also proposed to
improve the secrecy of the system by minimizing the eavesdropping rate.
Performances of these schemes are compared with two passive eavesdropping
scenarios in which the eavesdropper performs selection and maximal ratio
combining on the relayed links. A realistic channel model with independent
non-identical links between nodes and direct links from the source to both the
destination and eavesdropper are assumed. Closed-form expressions for the
secrecy outage probability (SOP) of these schemes in Rayleigh fading channel
are obtained. It is shown that the relay selection by the proactive
eavesdropper is most detrimental to the system as not only the SOP increases
with the increase in the number of relays, but its diversity also remains
unchanged.Comment: 6 pages, 4 figures, conference- GLOBECOM 1
Secure Communications in NOMA System: Subcarrier Assignment and Power Allocation
Secure communication is a promising technology for wireless networks because
it ensures secure transmission of information. In this paper, we investigate
the joint subcarrier (SC) assignment and power allocation problem for
non-orthogonal multiple access (NOMA) amplify-and-forward two-way relay
wireless networks, in the presence of eavesdroppers. By exploiting cooperative
jamming (CJ) to enhance the security of the communication link, we aim to
maximize the achievable secrecy energy efficiency by jointly designing the SC
assignment, user pair scheduling and power allocation. Assuming the perfect
knowledge of the channel state information (CSI) at the relay station, we
propose a low-complexity subcarrier assignment scheme (SCAS-1), which is
equivalent to many-to-many matching games, and then SCAS-2 is formulated as a
secrecy energy efficiency maximization problem. The secure power allocation
problem is modeled as a convex geometric programming problem, and then solved
by interior point methods. Simulation results demonstrate that the
effectiveness of the proposed SSPA algorithms under scenarios of using and not
using CJ, respectively
Multi-cell Hybrid Millimeter Wave Systems: Pilot Contamination and Interference Mitigation
In this paper, we investigate the system performance of a multi-cell
multi-user (MU) hybrid millimeter wave (mmWave) communications in a
multiple-input multiple-output (MIMO) network. Due to the reuse of pilot
symbols among different cells, the performance of channel estimation is
expected to be degraded by pilot contamination, which is considered as a
fundamental performance bottleneck of conventional multicell MU massive MIMO
networks. To analyze the impact of pilot contamination to the system
performance, we first derive the closed-form approximation of the normalized
mean squared error (MSE) of the channel estimation algorithm proposed in [2]
over Rician fading channels. Our analytical and simulation results show that
the channel estimation error incurred by the impact of pilot contamination and
noise vanishes asymptotically with an increasing number of antennas equipped at
each radio frequency (RF) chain at the desired BS. Furthermore, by adopting
zero-forcing (ZF) precoding in each cell for downlink transmission, we derive a
tight closed-form approximation of the average achievable rate per user. Our
results unveil that the intra-cell interference and inter-cell interference
caused by pilot contamination over Rician fading channels can be mitigated
effectively by simply increasing the number of antennas equipped at the desired
BS.Comment: To appear in IEEE Transactions on Communications. 15 pages, 7 figure
Safeguarding Wireless Network with UAVs: A Physical Layer Security Perspective
Integrating unmanned aerial vehicles (UAVs) into future wireless systems such
as the fifth-generation (5G) cellular network is anticipated to bring
significant benefits for both UAV and telecommunication industries. Generally
speaking, UAVs can be used as new aerial platforms in the cellular network to
provide communication services for terrestrial users, or become new aerial
users of the cellular network served by the terrestrial base stations. Due to
their high altitude, UAVs usually have dominant line-of-sight (LoS) channels
with the ground nodes, which, however, pose new security challenges to future
wireless networks with widely deployed UAVs. On one hand, UAV-ground
communications are more prone than terrestrial communications to eavesdropping
and jamming attacks by malicious nodes on the ground. On the other hand,
compared to malicious ground nodes, malicious UAVs can launch more effective
eavesdropping and jamming attacks to terrestrial communications. Motivated by
the above, in this article, we aim to identify such new issues from a
physical-layer security viewpoint and propose novel solutions to tackle them
efficiently. Numerical results are provided to validate their effectiveness and
promising directions for future research are also discussed.Comment: Accepted by IEEE Wireless Communications. In this article, we focus
on addressing two new and challenging security issues arising from the
LoS-dominant UAV-ground channels in future wireless networks, from a PHY
design perspectiv
Data-Aided Secure Massive MIMO Transmission with Active Eavesdropping
In this paper, we study the design of secure communication for time division
duplexing multi-cell multi-user massive multiple-input multiple-output (MIMO)
systems with active eavesdropping. We assume that the eavesdropper actively
attacks the uplink pilot transmission and the uplink data transmission before
eavesdropping the downlink data transmission phase of the desired users. We
exploit both the received pilots and data signals for uplink channel
estimation. We show analytically that when the number of transmit antennas and
the length of the data vector both tend to infinity, the signals of the desired
user and the eavesdropper lie in different eigenspaces of the received signal
matrix at the base station if their signal powers are different. This finding
reveals that decreasing (instead of increasing) the desire user's signal power
might be an effective approach to combat a strong active attack from an
eavesdropper. Inspired by this result, we propose a data-aided secure downlink
transmission scheme and derive an asymptotic achievable secrecy sum-rate
expression for the proposed design. Numerical results indicate that under
strong active attacks, the proposed design achieves significant secrecy rate
gains compared to the conventional design employing matched filter precoding
and artificial noise generation.Comment: Accepted by ICC'1
Optimal Transmit Antenna Selection for Massive MIMO Wiretap Channels
In this paper, we study the impacts of transmit antenna selection on the
secrecy performance of massive MIMO systems. We consider a wiretap setting in
which a fixed number of transmit antennas are selected and then confidential
messages are transmitted over them to a multi-antenna legitimate receiver while
being overheard by a multi-antenna eavesdropper. For this setup, we derive an
accurate approximation of the instantaneous secrecy rate. Using this
approximation, it is shown that in some wiretap settings under antenna
selection the growth in the number of active antennas enhances the secrecy
performance of the system up to some optimal number and degrades it when this
optimal number is surpassed. This observation demonstrates that antenna
selection in some massive MIMO settings not only reduces the RF-complexity, but
also enhances the secrecy performance. We then consider various scenarios and
derive the optimal number of active antennas analytically using our
large-system approximation. Numerical investigations show an accurate match
between simulations and the analytic results.Comment: Accepted for publication in IEEE JSAC special issue on "Physical
Layer Security for 5G Wireless Networks"; 11 pages, 8 figure