37 research outputs found
Secure Multiuser Communications in Wireless Sensor Networks with TAS and Cooperative Jamming
In this paper, we investigate the secure transmission in wireless sensor networks (WSNs) consisting of one multiple-antenna base station (BS), multiple single-antenna legitimate users, one single-antenna eavesdropper and one multiple-antenna cooperative jammer. In an effort to reduce the scheduling complexity and extend the battery lifetime of the sensor nodes, the switch-and-stay combining (SSC) scheduling scheme is exploited over the sensor nodes. Meanwhile, transmit antenna selection (TAS) is employed at the BS and cooperative jamming (CJ) is adopted at the jammer node, aiming at achieving a satisfactory secrecy performance. Moreover, depending on whether the jammer node has the global channel state information (CSI) of both the legitimate channel and the eavesdropper's channel, it explores a zero-forcing beamforming (ZFB) scheme or a null-space artificial noise (NAN) scheme to confound the eavesdropper while avoiding the interference to the legitimate user. Building on this, we propose two novel hybrid secure transmission schemes, termed TAS-SSC-ZFB and TAS-SSC-NAN, for WSNs. We then derive the exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput of both schemes to characterize the secrecy performance. Using these closed-form expressions, we further determine the optimal switching threshold and obtain the optimal power allocation factor between the BS and jammer node for both schemes to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for both schemes. Numerical results are provided to verify the theoretical analysis and illustrate the impact of key system parameters on the secrecy performance.This work was supported by the National Science Foundation of China (No. 61501507), and the Jiangsu Provincial Natural Science Foundation of China (No. BK20150719). The work of Nan Yang is supported by the Australian Research Council Discovery Project (DP150103905)
A Survey of Physical Layer Security Techniques for 5G Wireless Networks and Challenges Ahead
Physical layer security which safeguards data confidentiality based on the
information-theoretic approaches has received significant research interest
recently. The key idea behind physical layer security is to utilize the
intrinsic randomness of the transmission channel to guarantee the security in
physical layer. The evolution towards 5G wireless communications poses new
challenges for physical layer security research. This paper provides a latest
survey of the physical layer security research on various promising 5G
technologies, including physical layer security coding, massive multiple-input
multiple-output, millimeter wave communications, heterogeneous networks,
non-orthogonal multiple access, full duplex technology, etc. Technical
challenges which remain unresolved at the time of writing are summarized and
the future trends of physical layer security in 5G and beyond are discussed.Comment: To appear in IEEE Journal on Selected Areas in Communication
Physical Layer Service Integration in 5G: Potentials and Challenges
High transmission rate and secure communication have been identified as the
key targets that need to be effectively addressed by fifth generation (5G)
wireless systems. In this context, the concept of physical-layer security
becomes attractive, as it can establish perfect security using only the
characteristics of wireless medium. Nonetheless, to further increase the
spectral efficiency, an emerging concept, termed physical-layer service
integration (PHY-SI), has been recognized as an effective means. Its basic idea
is to combine multiple coexisting services, i.e., multicast/broadcast service
and confidential service, into one integral service for one-time transmission
at the transmitter side. This article first provides a tutorial on typical
PHY-SI models. Furthermore, we propose some state-of-the-art solutions to
improve the overall performance of PHY-SI in certain important communication
scenarios. In particular, we highlight the extension of several concepts
borrowed from conventional single-service communications, such as artificial
noise (AN), eigenmode transmission etc., to the scenario of PHY-SI. These
techniques are shown to be effective in the design of reliable and robust
PHY-SI schemes. Finally, several potential research directions are identified
for future work.Comment: 12 pages, 7 figure
An Overview of Physical Layer Security with Finite-Alphabet Signaling
Providing secure communications over the physical layer with the objective of
achieving perfect secrecy without requiring a secret key has been receiving
growing attention within the past decade. The vast majority of the existing
studies in the area of physical layer security focus exclusively on the
scenarios where the channel inputs are Gaussian distributed. However, in
practice, the signals employed for transmission are drawn from discrete signal
constellations such as phase shift keying and quadrature amplitude modulation.
Hence, understanding the impact of the finite-alphabet input constraints and
designing secure transmission schemes under this assumption is a mandatory step
towards a practical implementation of physical layer security. With this
motivation, this article reviews recent developments on physical layer security
with finite-alphabet inputs. We explore transmit signal design algorithms for
single-antenna as well as multi-antenna wiretap channels under different
assumptions on the channel state information at the transmitter. Moreover, we
present a review of the recent results on secure transmission with discrete
signaling for various scenarios including multi-carrier transmission systems,
broadcast channels with confidential messages, cognitive multiple access and
relay networks. Throughout the article, we stress the important behavioral
differences of discrete versus Gaussian inputs in the context of the physical
layer security. We also present an overview of practical code construction over
Gaussian and fading wiretap channels, and we discuss some open problems and
directions for future research.Comment: Submitted to IEEE Communications Surveys & Tutorials (1st Revision
Towards an enhanced noncoherent massive MU-MIMO system
PhD ThesisMany multiple-input multiple-output (MIMO) downlink transmission schemes assume
channel state information (CSI) is available at the receiver/transmitter. In
practice, knowledge of CSI is often obtained by using pilot symbols transmitted
periodically. However, for some systems, due to high mobility and the cost of
channel training and estimation, CSI acquisition is not always feasible. The problem
becomes even more difficult when many antennas are used in the system and
the channel is changing very rapidly before training is completed. Moreover, as
the number of transmit/receive antennas grows large, the number of pilot symbols,
system overheads, latency, and power consumption will grow proportionately
and thereby the system becomes increasingly complex. As an alternative, a noncoherent
system may be used wherein the transmitter/receiver does not need any
knowledge of the CSI to perform precoding or detection. This thesis focuses on
the design of a noncoherent downlink transmission system to jointly improve the
performance and achieve a simple low complexity transmission scheme in three
MIMO system scenarios: low rate differential spacetime block coding (STBC) in a
downlink multiuser (MU-MIMO) system; high rate differential algebraic STBC in
a downlink MU-MIMO system; and differential downlink transmission in a massive
MU-MIMO system. Three novel design methods for each of these systems are
proposed and analysed thoroughly.
For the MIMO system with a low rate noncoherent scheme, a differential STBC
MU-MIMO system with a downlink transmission scheme is considered. Specifically,
downlink precoding combined with differential modulation (DM) is used
to shift the complexity from the receivers to the transmitter. The block diagonalization
(BD) precoding scheme is used to cancel co-channel interference (CCI) in
addition to exploiting its advantage of enhancing diversity. Since the BD scheme
requires channel knowledge at the transmitter, the downlink spreading technique
along with DM is also proposed, which does not require channel knowledge neither
at the transmitter nor at the receivers. The orthogonal spreading (OS) scheme is
employed to have similar principle as code division multiple access (CDMA) multiplexing
scheme in order to eliminate the interference between users. As a STBC
scheme, the Alamouti code is used that can be encoded/decoded using DM thereby
eliminating the need for channel knowledge at the receiver. The proposed schemes
yield low complexity transceivers while providing good performance.
For the MIMO system with a high rate noncoherent scheme, a differential STBC
MU-MIMO system that operates at a high data rate is considered. In particular,
a full-rate full-diversity downlink algebraic transmission scheme combined with a
differential STBC systems is proposed. To achieve this, perfect algebraic space
time codes and Cayley differential (CD) transforms are employed. Since CSI is
not needed at the differential receiver, differential schemes are ideal for multiuser
systems to shift the complexity from the receivers to the transmitter, thus simplifying
user equipment. Furthermore, OS matrices are employed at the transmitter to
separate the data streams of different users and enable simple single user decoding.
In the OS scheme, the transmitter does not require any knowledge of the CSI to
separate the data streams of multiple users; this results in a system which does not
need CSI at either end. With this system, to limit the number of possible codewords,
a sphere decoder (SD) is used to decode the signals at the receiving end.
The proposed scheme yields low complexity transceivers while providing full-rate
full-diversity system with good performance.
Lastly, a differential downlink transmission scheme is proposed for a massive MIMO
system without explicit channel estimation. In particular, a downlink precoding
technique combined with a differential encoding scheme is used to simplify the
overall system complexity. A novel precoder is designed which, with a large number
of transmit antennas, can effectively precancel the multiple access interference
(MAI) for each user, thus enhancing the system performance. Maximising the worst
case signal-to-interference-plus-noise ratio (SINR) is adopted to optimise the precoder
for the users in which full power space profile (PSP) knowledge is available to
the base station (BS). Also, two suboptimal solutions based on the matched and the
orthogonality approach of PSP are provided to separate the data streams of multiple
users. The decision feedback differential detection (DFDD) technique is employed
to further improve the performance.
In summary, the proposed methods eliminate MAI, enhance system performance,
and achieve a simple low complexity system. Moreover, transmission overheads
are significantly reduced, the proposed methods avoid explicit channel estimation
at both ends.King Fahad Security Collage at the Ministry of Interior - Saudi Arabia
An Overview of Physical Layer Security with Finite Alphabet Signaling
Providing secure communications over the physical layer with the objective of achieving secrecy without requiring a secret key has been receiving growing attention within the past decade. The vast majority of the existing studies in the area of physical layer security focus exclusively on the scenarios where the channel inputs are Gaussian distributed. However, in practice, the signals employed for transmission are drawn from discrete signal constellations such as phase shift keying and quadrature amplitude modulation. Hence, understanding the impact of the finite-alphabet input constraints and designing secure transmission schemes under this assumption is a mandatory step towards a practical implementation of physical layer security. With this motivation, this article reviews recent developments on physical layer security with finite-alphabet inputs. We explore transmit signal design algorithms for single-antenna as well as multi-antenna wiretap channels under different assumptions on the channel state information at the transmitter. Moreover, we present a review of the recent results on secure transmission with discrete signaling for various scenarios including multi-carrier transmission systems, broadcast channels with confidential messages, cognitive multiple access and relay networks. Throughout the article, we stress the important behavioral differences of discrete versus Gaussian inputs in the context of the physical layer security. We also present an overview of practical code construction over Gaussian and fading wiretap channels, and discuss some open problems and directions for future research