252 research outputs found
Secret-Message Transmission by Echoing Encrypted Probes -- STEEP
This paper examines the properties of the lower and upper bounds established
by Maurer, Ahlswede and Csiszar (MAC) for secret-key capacity in the case of
channel probing over single-input and single-output (SISO) channels. Inspired
by the insights into MAC's bounds, a scheme called secret-message transmission
by echoing encrypted probes (STEEP) is proposed. STEEP consists of two phases:
in phase 1, Alice sends random probes over a probing channel to Bob; in phase
2, Bob echoes back an estimated version of the probes, but encrypted by a
secret, over a high-quality return channel. Provided that Eve is unable to
obtain the exact probes transmitted by Alice in phase 1, STEEP guarantees a
positive secrecy rate from Bob to Alice over the return channel even if Eve's
channel strength during channel probing is stronger than Bob's. STEEP is
applicable to both physical layer and upper layers in connected networks
High Rate/Low Complexity Space-Time Block Codes for 2x2 Reconfigurable MIMO Systems
In this paper, we propose a full-rate full-diversity space-time block code
(STBC) for 2x2 reconfigurable multiple-input multiple-output (MIMO) systems
that require a low complexity maximum likelihood (ML) detector. We consider a
transmitter equipped with a linear antenna array where each antenna element can
be independently configured to create a directive radiation pattern toward a
selected direction. This property of transmit antennas allow us to increase the
data rate of the system, while reducing the computational complexity of the
receiver. The proposed STBC achieves a coding rate of two in a 2x2 MIMO system
and can be decoded via an ML detector with a complexity of order M, where M is
the cardinality of the transmitted symbol constellation. Our simulations
demonstrate the efficiency of the proposed code compared to existing STBCs in
the literature.Comment: arXiv admin note: text overlap with arXiv:1505.0646
High-Rate Space Coding for Reconfigurable 2x2 Millimeter-Wave MIMO Systems
Millimeter-wave links are of a line-of-sight nature. Hence, multiple-input
multiple-output (MIMO) systems operating in the millimeter-wave band may not
achieve full spatial diversity or multiplexing. In this paper, we utilize
reconfigurable antennas and the high antenna directivity in the millimeter-wave
band to propose a rate-two space coding design for 2x2 MIMO systems. The
proposed scheme can be decoded with a low complexity maximum-likelihood
detector at the receiver and yet it can enhance the bit-error-rate performance
of millimeter-wave systems compared to traditional spatial multiplexing
schemes, such as the Vertical Bell Laboratories Layered Space-Time Architecture
(VBLAST). Using numerical simulations, we demonstrate the efficiency of the
proposed code and show its superiority compared to existing rate-two space-time
block codes
DC-Informative Joint Color-Frequency Modulation for Visible Light Communications
In this paper, we consider the problem of constellation design for a visible
light communication (VLC) system using red/green/blue light-emitting diodes
(RGB LED), and propose a method termed DC-informative joint color-frequency
modulation (DCI-JCFM). This method jointly utilizes available diversity
resources including different optical wavelengths, multiple baseband
subcarriers, and adaptive DC-bias. Constellation is designed in a high
dimensional space, where the compact sphere packing advantage over lower
dimensional counterparts is utilized. Taking into account multiple practical
illumination constraints, a non-convex optimization problem is formulated,
seeking the least error rate with a fixed spectral efficiency. The proposed
scheme is compared with a decoupled scheme, where constellation is designed
separately for each LED. Notable gains for DCI-JCFM are observed through
simulations where balanced, unbalanced and very unbalanced color illuminations
are considered.Comment: submitted to Journal of Lightwave Technology, Aug. 5th 201
Hybrid Millimeter-Wave Systems: A Novel Paradigm for HetNets
Heterogeneous Networks (HetNets) are known to enhance the bandwidth
efficiency and throughput of wireless networks by more effectively utilizing
the network resources. However, the higher density of users and access points
in HetNets introduces significant inter-user interference that needs to be
mitigated through complex and sophisticated interference cancellation schemes.
Moreover, due to significant channel attenuation and presence of hardware
impairments, e.g., phase noise and amplifier nonlinearities, the vast bandwidth
in the millimeter-wave band has not been fully utilized to date. In order to
enable the development of multi-Gigabit per second wireless networks, we
introduce a novel millimeter-wave HetNet paradigm, termed hybrid HetNet, which
exploits the vast bandwidth and propagation characteristics in the 60 GHz and
70-80 GHz bands to reduce the impact of interference in HetNets. Simulation
results are presented to illustrate the performance advantage of hybrid HetNets
with respect to traditional networks. Next, two specific transceiver structures
that enable hand-offs from the 60 GHz band, i.e., the V-band to the 70-80 GHz
band, i.e., the E-band, and vice versa are proposed. Finally, the practical and
regulatory challenges for establishing a hybrid HetNet are outlined.Comment: 12 pages, 5 Figures, IEEE Communication Magazine. In pres
Optimal Pilots for Anti-Eavesdropping Channel Estimation
Anti-eavesdropping channel estimation (ANECE) is a method that uses specially
designed pilot signals to allow two or more full-duplex radio devices each with
one or more antennas to estimate their channel state information (CSI)
consistently and at the same time prevent eavesdropper (Eve) with any number of
antennas from obtaining its CSI consistently. This paper presents optimal
designs of the pilots for ANECE based on two criteria. The first is the mean
squared error (MSE) of channel estimation for the users, and the second is the
mutual information (MI) between the pilot-driven signals observed by the users.
Closed-form optimal pilots are shown under the sum-MSE and sum-MI criteria
subject to a symmetric and isotropic condition. Algorithms for computing the
optimal pilots are shown for general cases. Fairness issues for three or more
users are discussed. The performances of different designs are compared
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