292 research outputs found
Beam domain secure transmission for massive MIMO communications
We investigate the optimality and power allocation algorithm of beam domain
transmission for single-cell massive multiple-input multiple-output (MIMO)
systems with a multi-antenna passive eavesdropper. Focusing on the secure
massive MIMO downlink transmission with only statistical channel state
information of legitimate users and the eavesdropper at base station, we
introduce a lower bound on the achievable ergodic secrecy sum-rate, from which
we derive the condition for eigenvectors of the optimal input covariance
matrices. The result shows that beam domain transmission can achieve optimal
performance in terms of secrecy sum-rate lower bound maximization. For the case
of single-antenna legitimate users, we prove that it is optimal to allocate no
power to the beams where the beam gains of the eavesdropper are stronger than
those of legitimate users in order to maximize the secrecy sum-rate lower
bound. Then, motivated by the concave-convex procedure and the large dimension
random matrix theory, we develop an efficient iterative and convergent
algorithm to optimize power allocation in the beam domain. Numerical
simulations demonstrate the tightness of the secrecy sum-rate lower bound and
the near-optimal performance of the proposed iterative algorithm
Power Efficient Resource Allocation for Full-Duplex Radio Distributed Antenna Networks
In this paper, we study the resource allocation algorithm design for
distributed antenna multiuser networks with full-duplex (FD) radio base
stations (BSs) which enable simultaneous uplink and downlink communications.
The considered resource allocation algorithm design is formulated as an
optimization problem taking into account the antenna circuit power consumption
of the BSs and the quality of service (QoS) requirements of both uplink and
downlink users. We minimize the total network power consumption by jointly
optimizing the downlink beamformer, the uplink transmit power, and the antenna
selection. To overcome the intractability of the resulting problem, we
reformulate it as an optimization problem with decoupled binary selection
variables and non-convex constraints. The reformulated problem facilitates the
design of an iterative resource allocation algorithm which obtains an optimal
solution based on the generalized Bender's decomposition (GBD) and serves as a
benchmark scheme. Furthermore, to strike a balance between computational
complexity and system performance, a suboptimal algorithm with polynomial time
complexity is proposed. Simulation results illustrate that the proposed GBD
based iterative algorithm converges to the global optimal solution and the
suboptimal algorithm achieves a close-to-optimal performance. Our results also
demonstrate the trade-off between power efficiency and the number of active
transmit antennas when the circuit power consumption is taken into account. In
particular, activating an exceedingly large number of antennas may not be a
power efficient solution for reducing the total system power consumption. In
addition, our results reveal that FD systems facilitate significant power
savings compared to traditional half-duplex systems, despite the non-negligible
self-interference.Comment: Submitted for possible journal publicatio
Compressive Massive Random Access for Massive Machine-Type Communications (mMTC)
In future wireless networks, one fundamental challenge for massive
machine-type communications (mMTC) lies in the reliable support of massive
connectivity with low latency. Against this background, this paper proposes a
compressive sensing (CS)-based massive random access scheme for mMTC by
leveraging the inherent sporadic traffic, where both the active devices and
their channels can be jointly estimated with low overhead. Specifically, we
consider devices in the uplink massive random access adopt pseudo random
pilots, which are designed under the framework of CS theory. Meanwhile, the
massive random access at the base stations (BS) can be formulated as the sparse
signal recovery problem by leveraging the sparse nature of active devices.
Moreover, by exploiting the structured sparsity among different receiver
antennas and subcarriers, we develop a distributed multiple measurement vector
approximate message passing (DMMV-AMP) algorithm for further improved
performance. Additionally, the state evolution (SE) of the proposed DMMV-AMP
algorithm is derived to predict the performance. Simulation results demonstrate
the superiority of the proposed scheme, which exhibits a good tightness with
the theoretical SE.Comment: This paper has been accepted by 2018 IEEE GlobalSI
UAV-Enabled Mobile Edge Computing: Offloading Optimization and Trajectory Design
With the emergence of diverse mobile applications (such as augmented
reality), the quality of experience of mobile users is greatly limited by their
computation capacity and finite battery lifetime. Mobile edge computing (MEC)
and wireless power transfer are promising to address this issue. However, these
two techniques are susceptible to propagation delay and loss. Motivated by the
chance of short-distance line-of-sight achieved by leveraging unmanned aerial
vehicle (UAV) communications, an UAV-enabled wireless powered MEC system is
studied. A power minimization problem is formulated subject to the constraints
on the number of the computation bits and energy harvesting causality. The
problem is non-convex and challenging to tackle. An alternative optimization
algorithm is proposed based on sequential convex optimization. Simulation
results show that our proposed design is superior to other benchmark schemes
and the proposed algorithm is efficient in terms of the convergence.Comment: This paper has been accepted by IEEE ICC 201
Computation Rate Maximization in UAV-Enabled Wireless Powered Mobile-Edge Computing Systems
Mobile edge computing (MEC) and wireless power transfer (WPT) are two
promising techniques to enhance the computation capability and to prolong the
operational time of low-power wireless devices that are ubiquitous in Internet
of Things. However, the computation performance and the harvested energy are
significantly impacted by the severe propagation loss. In order to address this
issue, an unmanned aerial vehicle (UAV)-enabled MEC wireless powered system is
studied in this paper. The computation rate maximization problems in a
UAV-enabled MEC wireless powered system are investigated under both partial and
binary computation offloading modes, subject to the energy harvesting causal
constraint and the UAV's speed constraint. These problems are non-convex and
challenging to solve. A two-stage algorithm and a three-stage alternative
algorithm are respectively proposed for solving the formulated problems. The
closed-form expressions for the optimal central processing unit frequencies,
user offloading time, and user transmit power are derived. The optimal
selection scheme on whether users choose to locally compute or offload
computation tasks is proposed for the binary computation offloading mode.
Simulation results show that our proposed resource allocation schemes
outperforms other benchmark schemes. The results also demonstrate that the
proposed schemes converge fast and have low computational complexity.Comment: This paper has been accepted by IEEE JSA
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
MIMO-OFDM Scheme design for Medium Voltage Underground Cables based Power Line Communication
Power line communication (PLC) provides intelligent electrical functions such
as power quality measurement, fault surveys, and remote control of electrical
network. However, most of research works have been done in low voltage (LV)
scenario due to the fast development of in-home PLC. The aim of this paper is
to design a MIMO-OFDM based transmission link under medium voltage (MV)
underground power line channel and evaluate the performance. The MIMO channel
is modeled as a modified multipath model in the presence of impulsive noise and
background noise. Unlike most literatures on MIMO power line transmission, we
adopt spatial multiplexing instead of diversity to increase the transmission
rate in this paper. The turbo coding method originally designed for LV power
line communication is used in the proposed transmission system. By comparing
the BER performance of MIMO-OFDM system with and without the turbo coding, we
evaluate its applicability in MV power line communication. The effect of
frequency band varying on the PLC system's performance is also investigated.Comment: To appear in IEEE WCSP'1
Optimal Detection of UAV's Transmission with Beam Sweeping in Wireless Networks
In this work, an detection strategy based on multiple antennas with beam
sweeping is developed to detect UAV's potential transmission in wireless
networks. Specifically, suspicious angle range where the UAV may present is
divided into different sectors to potentially increase detection accuracy by
using beamforming gain. We then develop the optimal detector and derive its
detection error probability in a closed-form expression. We also utilize the
Pinsker's inequality and Kullback-Leibler divergence to yield low-complex
approximation for the detection error probability, based on which we obtain
some significant insights on the detection performance. Our examination shows
that there exists an optimal number of sectors that can minimize the detection
error probability in some scenarios (e.g., when the number of measurements is
limited). Intuitively, this can be explained by the fact that there exists an
optimal accuracy of the telescope used to find an object in the sky within
limited time period
Two High-performance Schemes of Transmit Antenna Selection for Secure Spatial Modulation
In this paper, a secure spatial modulation (SM) system with artificial noise
(AN)-aided is investigated. To achieve higher secrecy rate (SR) in such a
system, two high-performance schemes of transmit antenna selection (TAS),
leakage-based and maximum secrecy rate (Max-SR), are proposed and a generalized
Euclidean distance-optimized antenna selection (EDAS) method is designed. From
simulation results and analysis, the four TAS schemes have an decreasing order:
Max-SR, leakage-based, generalized EDAS, and random (conventional), in terms of
SR performance. However, the proposed Max-SR method requires the exhaustive
search to achieve the optimal SR performance, thus its complexity is extremely
high as the number of antennas tends to medium and large scale. The proposed
leakage-based method approaches the Max-SR method with much lower complexity.
Thus, it achieves a good balance between complexity and SR performance. In
terms of bit error rate (BER), their performances are in an increasing order:
random, leakage-based, Max-SR, and generalized EDAS
Pilot Spoofing Attack by Multiple Eavesdroppers
In this paper, we investigate the design of a pilot spoofing attack (PSA)
carried out by multiple single-antenna eavesdroppers (Eves) in a downlink
time-division duplex (TDD) system, where a multiple antenna base station (BS)
transmits confidential information to a single-antenna legitimate user (LU).
During the uplink channel training phase, multiple Eves collaboratively impair
the channel acquisition of the legitimate link, aiming at maximizing the
wiretapping signal-to-noise ratio (SNR) in the subsequent downlink data
transmission phase. Two different scenarios are investigated: (1) the BS is
unaware of the PSA, and (2) the BS attempts to detect the presence of the PSA.
For both scenarios, we formulate wiretapping SNR maximization problems. For the
second scenario, we also investigate the probability of successful detection
and constrain it to remain below a pre-designed threshold. The two resulting
optimization problems can be unified into a more general non-convex
optimization problem, and we propose an efficient algorithm based on the
minorization-maximization (MM) method and the alternating direction method of
multipliers (ADMM) to solve it. The proposed MM-ADMM algorithm is shown to
converge to a stationary point of the general problem. In addition, we propose
a semidefinite relaxation (SDR) method as a benchmark to evaluate the
efficiency of the MM-ADMM algorithm. Numerical results show that the MM-ADMM
algorithm achieves near-optimal performance and is computationally more
efficient than the SDRbased method.Comment: Accepted by IEEE Transaction on Wireless Communication
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