Xinrong Guan

On the Mutual Information and Precoding for Spatial Modulation with Finite Alphabet

In this letter, we investigate the effect of finite alphabet inputs on the performance of spatial modulation (SM) for multiple-input-single-output (MISO) channels. The closed-form expression of the mutual information is first derived in an information-theoretic framework. With careful analysis of the expression, we develop a precoding scheme to improve the performance of SM. Utilizing the theory of traditional constellation design, the precoding coefficient is obtained by maximizing the minimum Euclidean distance. Numerical results demonstrate substantial difference in the mutual information between SM with finite alphabet inputs and SM with Gaussian inputs, and show that our precoding scheme achieves significant gains.

Outage Performance of Statistical CSI Assisted Cognitive Relay with Interference from Primary User

This work has studied the outage performance of amplify-and-forward (AF) relaying in underlay spectrum sharing systems with interference from primary user (PU). To reduce the complexity and improve the feasibility, two schemes using statistical channel state information (CSI) of interference links are proposed. For each scheme, the closed-form expressions for outage probability of secondary user (SU) and PU are derived, as well as the asymptotic expressions and diversity order. The impact of using statistical CSI instead of instantaneous CSI has been evaluated through the comparison with existing scheme. The analytical results and the simulation results are in excellent agrement confirming the effectiveness of the analysis in this work.

On the secrecy mutual information of spatial modulation with finite alphabet

In this paper, the spatial modulation (SM) is considered as a novel physical layer technique to improve the physical layer security of wireless networks. Exploiting the index of antenna as an additional dimension to convey part of source information bits, SM helps to achieve multiplexing gain and realize higher data rates. Moreover, by properly designing the transmission signal, SM can also improve physical layer security. The secrecy mutual information of SM with finite alphabet input is derived in this work, and a preceding scheme is proposed to improve the physical layer security performance of SM. Analysis and numerical results verify the validity and effectiveness of the proposed scheme, and it also shows that the maximum achievable secrecy mutual information is the logarithm of the number of transmit antennas.

Increasing secrecy capacity via joint design of cooperative beamforming and jamming

In this paper, we propose a hybrid cooperative scheme to improve the secrecy rate for a cooperative network in presence of multiple relays. Each relay node transmits a mixed signal consisting of weighted source signal and intentional noise. The problem of power allocation and joint design of beamforming and jamming weights are investigated, and an iterative solution for the secrecy rate maximization problem is presented. The numerical results demonstrate that the proposed hybrid scheme further improves secrecy rate, as compared to traditional cooperative schemes.

Secure Transmission Design and Performance Analysis for Cooperation Exploring Outdated CSI

Under the assumption of outdated CSI, the transmission design and secrecy performance in cooperative networks is studied. Using the delay correlation model, the source first estimates the connection outage probability (COP) and secrecy outage probability (SOP), respectively, thus the secrecy information can be encoded into a Wyner code with proper rate pair. If the destination does not decode but the relay does, an opportunistic decode-and-forward (ODF) cooperation would be implemented to help the transmission. Some new insights into the secrecy performance of ODF are provided via the analysis of reliability-security tradeoff (RST) and secrecy throughput.

On the Reliability-Security Tradeoff and Secrecy Throughput in Cooperative ARQ

This work has studied the physical layer security in cooperative automatic-repeat-request (CARQ), under the assumption of no instantaneous channel state information (CSI) at legitimate users. Different from present works, this paper not only derives closed form expressions for connection outage probability (COP) and secrecy outage probability (SOP) to evaluate the reliability and security, respectively, but also first establishes the direct relationship between them via the reliability-security tradeoff (RST). Moreover, we present a novel formulation for secrecy throughput, which gives a more complete insight into the efficiency of CARQ achieving reliable and secure transmission.

Exploiting primary retransmission to improve secondary throughput by cognitive relaying with best-relay selection

In this paper, the authors propose two cognitive relaying schemes based on overlay and underlay, which exploit the cooperation opportunities inherent in primary retransmission to improve secondary throughput. If a primary signal is not decoded by the primary receiver (PR), a secondary user (SU) can be selected to relay it invisibly along with the primary retransmission. For overlay cognitive relaying, SUs intend to reduce primary retransmission time by relaying primary message, so that more access opportunities are available. While in underlay cognitive relaying, SU allocates part of its power to help primary user (PU) and the remaining power is used to transmit secondary message simultaneously. By controlling the phase of the relay signal, signals retransmitted from primary transmitter (PT) and SU can constructively combine at the PR. In both relaying schemes, we consider the best-relay selection as well. We define some novel metrics to evaluate the performance of PU and SU. For PU, we study the improvements in outage performance and average transmitting time per packet, while for SU, we consider the cooperation gain and cooperation efficiency, respectively. Theoretical analysis and numerical results verify the validity of both schemes, and a comparison is made between them.

Improving physical layer security in underlay D2D communication via Stackelberg game based power control

Device-to-Device (D2D) communication has advantages of improving the spectral resource efficiency. But unfortunately, it brings about interference and potential secrecy hazard. In this paper, a Stackelberg game based power control algorithm is provided to enhance the physical layer security underlaying D2D communication by utilizing the interference. Then, a mathematical model based on Stackelberg game is set up, in which we regard the secrecy energy efficiency as the utility function. After that, the existence and uniqueness of the Stackelberg Equilibrium is proved. In addition, a power control algorithm is offered, which can iteratively converge to the Stackelberg Equilibrium. Finally the simulation results show that by applying the provided algorithm, both the cellular user and the D2D pair have the secrecy energy efficiency improved.

Distributed beamforming for two-way amplify-and-forward relay in cooperative networks

Distributed beamforming is a promising technology in wireless communication. In this paper, we consider its application in the context of AF-based two-way relay. With a full CSI assumption, we make effort to maximize the sum-rate of source nodes S1 and S2 by optimizing the design of beamforming weight vector. However, an optimal closed form solution can not be derived for such a problem. Alternatively, we study two sub-optimal algorithms in the criterion of minimization of sum inverse-SNR and maximization of the minimum SNR. A discussion about their performance was presented at last, as well as their advantages and disadvantages.

Power allocation for improving physical layer security in D2D communication via stackelberg game

In this paper, we aim to improve the physical layer security for Device-to-device (D2D) communication underlaying cellular networks by allocating interference power elegantly, and the security issues of both cellular users and D2D pairs are taken into consideration simultaneously. First of all, the two-level sequential Stackelberg game is introduced to solve the above problem via power allocation, which can better describe the asymmetric competition between cellular users and D2D pairs. Moreover, the secrecy energy efficiency is defined as the utility function from the view of energy conservation. Then, an iterative power allocation algorithm is designed after the theoretical analysis. Finally, the simulation results show that both cellular users and D2D pairs have the security performance improved.