Pengcheng Mu

Secrecy Rate Maximization With Artificial-Noise-Aided Beamforming for MISO Wiretap Channels Under Secrecy Outage Constraint

The secrecy rate maximization with the artificial noise (AN) aided beamforming for the multipel-input-single-output (MISO) wiretap channel is addressed in this paper under the constraint of secrecy outage probability. The channel state information (CSI) of the main channel is assumed to be perfectly known while the CSI of the eavesdropper is modeled as a complex Gaussian random vector. The generalized AN scheme where the AN is not constrained to be orthogonal to the information-bearing signal is considered. The complete solution to the maximum achievable secrecy rate and the corresponding optimal power allocation between the information-bearing signal and the AN is obtained without making any approximation of the secrecy outage probability constraint. The result shows that the optimal AN is always orthogonal to the information-bearing signal.

Optimal Semiadaptive Transmission With Artificial-Noise-Aided Beamforming in MISO Wiretap Channels

This paper studies the design of artificial-noise-aided (AN-aided) secure transmission in slow-fading multiple-input-single-output (MISO) channels. We consider the scenario where a multiantenna transmitter sends messages to a single-antenna legitimate receiver in the presence of multiple noncolluding single-antenna eavesdroppers. It is assumed that the transmitter possesses instantaneous channel state information (CSI) of the legitimate channel but only the statistics of the eavesdroppers channels. Instead of adopting the well-known adaptive and nonadaptive transmission schemes, we consider the newly proposed semiadaptive scheme, in which the communication rate is fixed, and the secrecy rate is adaptively adjusted according to the legitimate channels CSI. Compared with the adaptive scheme, a major advantage of fixing the communication rate is that the codebook can be fixed, and thus, the encoder and decoder designs are both simplified. We consider a generalized AN-aided beamforming structure, which allows arbitrary beamforming direction. Specifically, we focus on the problem of maximizing the secrecy throughput on the premise of reliable and secure transmission. By solving this problem, the optimal beamforming direction, power-allocation parameters, and secrecy rate are derived in closed form, and the optimal communication rate is obtained numerically. Finally, simulation results are presented to show the performance of the semiadaptive scheme.

Robust MVDR beamforming based on covariance matrix reconstruction

The minimum variance distortionless response (MVDR) beamformer has better resolution and much better interference rejection capability than the data-independent beamformers. However, the former is more sensitive to errors, such as the steering vector errors caused by direction of arrival mismatch, imprecise array calibration or any other possible factors, especially in the case of high signal-to-noise ratio (SNR). A new robust MVDR beamformer against the general steering vector errors is proposed in this paper. This method is based on the reconstruction of the covariance matrix which aims to reduce the power of the signal of interest (SOI) in the covariance matrix. The eigenanalysis is used in the process of removing the SOI component and modifying the residual covariance matrix. Simulation results show that the proposed method has excellent signal-to-interference-plus-noise ratio (SINR) performance under the mismatch condition.

An extensible framework for fast prototyping of multiprocessor dataflow applications

As the number of cores continues to grow in both digital signal and general purpose processors, tools which perform automatic scheduling from model-based designs are of increasing interest. CAL is a new actor/dataflow oriented language that aims at helping the programmer to express the concurrency and parallelism that are very important aspects of embedded system design as we enter in the multicore era. The design framework is composed by the OpenDF simulation platform, by Cal2C and CAL2HDL code generators and by a multiprocessor scheduling tool called PREESM. Yet in this paper, a subset of CAL is used to describe the application such that the application is SDF. This SDF graph is one starting point of the workflow of PREESM (composed of several plug-ins) to be prototyped/distributed/scheduled over an IP-XACT multiprocessor platform description. The PREESM automatic scheduling consists in statically distributing the tasks that constitute an application between available cores in a multi-core architecture in order to minimize the final latency. This problem has been proven to be NP-complete. An IDCT 2D example will be used as test case of the full framework.

Practical Transmission Scheme With Fixed Communication Rate Under Constraints of Transmit Power and Secrecy Outage Probability

The issue of physical layer security in single-antenna wiretap channels with slow fading is addressed in this letter. With the assumption of perfect channel state information (CSI) about the main channel and statistical CSI about the eavesdroppers channel, we propose a new secure transmission scheme under the constraints of transmit power and secrecy outage probability (SOP). This scheme fixes the communication rate and adaptively adjusts the secrecy rate and the transmit power during transmission, which is different from the conventional adaptive and non-adaptive schemes in the literature. By fixing the communication rate, the proposed scheme fixes the length of codebook and thus simplifies the codebook design. Simulation results show that the proposed scheme performs well when the SOP constraint is strict.

A wireless secret key generation method based on Chinese remainder theorem in FDD systems

The wireless physical channel parameters are recently used to provide secret key. However, the key generation usually suffers from the quantization errors due to the noise, which decreases the key agreement ratio (KAR) between authorized users. Most existing approaches achieve high KAR by discarding some channel parameters which may lower the key generation efficiency and therefore lower the encryption strength. In the frequency-division duplex (FDD) systems, the number of reciprocal parameters, such as the multipath angle and delay, is limited. Therefore how to find a quantization method with high KAR and encryption strength is one of the major problems for secret key generation in FDD systems. In this paper, a robust quantization scheme based on grouping and shifting is proposed, in which all the available parameters are used for key generation. In addition, a key mapping method with error correction based on Chinese remainder theorem (CRT) is proposed to further improve the KAR performance. Simulations demonstrate the effectiveness of the proposed method.

Robust MVDR beamforming using the DOA matrix decomposition

The minimum variance distortionless response (MVDR) beamformer is very sensitive to errors, such as the the finite snapshots and the steering vector errors. A small mismatch can lead to serious degradation to its performance, especially at high signal-to-noise ratio(SNR). In this paper, a new robust MVDR beamformer is proposed. Our analysis starts from the physical meaning of the MVDR weight vector formula. Based on this analysis, DOA matrix is constructed in the single uniform linear array. Through the decomposition of this DOA matrix, we could obtain the actual signal modes contained in the covariance matrix of the snapshots. Then the weight vector could be modified to solve the robustness problem of MVDR beamforming. The computer simulation shows the effectiveness of this method.

Secrecy Rate Maximization With Uncoordinated Cooperative Jamming by Single-Antenna Helpers Under Secrecy Outage Probability Constraint

The issue of physical layer security for single-input-multiple-output (SIMO) wiretap channel with uncoordinated cooperative jamming (UCJ) is addressed in this letter, and we focus on power allocation in secrecy rate maximization (SRM) problem. Differing from the existing works, a practical UCJ scheme is proposed by using multiple single-antenna helpers where each helper transmits a jamming signal independently to confound the eavesdropper. Assuming that statistical channel state information (CSI) concerning the eavesdropper is available, a modified DC (difference of convex function) programming method is provided to solve the SRM problem under secrecy outage probability constraint and an achievable solution of power allocation is obtained. Numerical results show that the proposed scheme has satisfactory secrecy performance especially when the number of helpers is large.

Multiple Doppler shifts compensation and ICI elimination by beamforming in high-mobility OFDM systems

Although OFDM is an effective way to mitigate the multipath spread of the wireless channels by a simple equalization, it is very sensitive to Doppler effect. Doppler spreading due to the mobility of communication terminals destroys the orthogonality among the subcarriers, and results in intercarrier interference, which degrades the system performance. In this paper, we employ array beamforming and interference suppression to compensate multiple Doppler shifts in high-speed OFDM systems. The proposed method uses uniform circular array to separate different paths with unique Doppler shift, and then correct Doppler offsets in different paths respectively. This scheme not only eases channel estimation and equalization but also utilizes the multipath characteristics of wireless channel and provides Doppler diversity gains. Simulation results show that when sufficient elements were used, the proposed scheme can effectively combat the BER error floor in high-mobility scenario and have great performance enhancement over traditional methods.

Two-step transmission with artificial noise for secure wireless SIMO communications

The issue of physical layer security of the wireless single-input multiple-output (SIMO) system is addressed in this paper. We propose a two-step transmission scheme with artificial noise to improve the security and the scheme does not require the channel state information of the eavesdropper. In the first step, the destination which has multiple antennas generates a random reference symbol and artificial noise and transmits them in the direction of the source and its orthogonal space, respectively. The reference symbol is received by the source without being polluted by the artificial noise, while it is jammed by the artificial noise for the eavesdropper. In the second step, the symbol of the source is multiplied by the received reference symbol and then transmitted. Finally, the destination can directly estimate the symbol of the source using the reference symbol. However, the eavesdropper needs to additionally estimate the reference symbol for demodulating the symbol of the source, which usually obtains an inaccurate result due to the artificial noise. The information-theoretic security of our scheme is analyzed and a lower bound of the achievable secrecy rate is derived. The performance of the new scheme is compared with that of the traditional approach under different input signals through numerical simulations. The results show that the proposed scheme outperforms the traditional SIMO approach especially in the high SNR region.