2 research outputs found
Low-Complexity Linear Precoding for Secure Spatial Modulation
In this work, we investigate linear precoding for secure spatial modulation.
With secure spatial modulation, the achievable secrecy rate does not have an
easy-to-compute mathematical expression, and hence, has to be evaluated
numerically, which leads to high complexity in the optimal precoder design. To
address this issue, an accurate and analytical approximation of the secrecy
rate is derived in this work. Using this approximation as the objective
function, two low-complexity linear precoding methods based on gradient descend
(GD) and successive convex approximation (SCA) are proposed. The GD-based
method has much lower complexity but usually converges to a local optimum. On
the other hand, the SCA-based method uses semi-definite relaxation to deal with
the non-convexity in the precoder optimization problem and achieves
near-optimal solution. Compared with the existing GD-based precoder design in
the literature that directly uses the exact and numerically evaluated secrecy
capacity as the objective function, the two proposed designs have significantly
lower complexity. Our SCA-based design even achieves a higher secrecy rate than
the existing GD-based design.Comment: 11pages, 8figure
Precoding and Transmit Antenna Subarray Selection for Secure Hybrid Spatial Modulation
Spatial modulation (SM) is a particularly important form of
multiple-input-multiple-output (MIMO). Unlike traditional MIMO, it uses both
modulation symbols and antenna indices to carry information. In this paper, to
avoid the high cost and circuit complexity of fully-digital SM, we mainly
consider the hybrid SM system with a hybrid precoding transmitter architecture,
combining a digital precoder and an analog precoder. Here, the
partially-connected structure is adopted with each radio frequency chain (RF)
being connected to a transmit antenna subarray (TAS). In such a system, we made
an investigation of secure hybrid precoding and transmit antenna subarray
selection (TASS) methods. Two hybrid precoding methods, called maximizing the
approximate secrecy rate (SR) via gradient ascent (Max-ASR-GA) and maximizing
the approximate SR via alternating direction method of multipliers
(Max-ASR-ADMM), are proposed to improve the SR performance. As for TASS, a
high-performance method of maximizing the approximate SR (Max-ASR) TASS method
is first presented. To reduce its high complexity, two low-complexity TASS
methods, namely maximizing the eigenvalue (Max-EV) and maximizing the product
of signal-to-interference-plus-noise ratio and artificial
noise-to-signal-plus-noise ratio (Max-P-SINR-ANSNR), are proposed. Simulation
results will demonstrate that the proposed Max-ASR-GA and Max-ASR-ADMM hybrid
precoders harvest substantial SR performance gains over existing method. For
TASS, the proposed three methods Max-ASR, Max-EV, and Max-P-SINR-ANSNR perform
better than existing leakage method. Particularly, the proposed Max-EV and
Max-P-SINR-ANSNR is low-complexity at the expense of a little performance loss
compared with Max-ASR.Comment: 13 pages, 8 figure