Jian Ouyang

Joint Beamforming and Power Control for Device-to-Device Communications Underlaying Cellular Networks

In this paper, we address the issue of joint beamforming (BF) and power control for a device-to-device (D2D) communication underlaying cellular network, where the wireless channels of the D2D link and the base station to user equipment link experience Rician and correlated Rayleigh fading, respectively. Based on the property of the integral network, we first formulate a constrained optimization problem to minimize the total transmit power of the devices in the network, while meeting the quality-of-service requirement of both the D2D and cellular users and suppressing the mutual interference to a certain level. Then, by adopting the available statistical channel state information and proposing an approximation method to relax the constraints, a support-vector-machine-based algorithm is presented to solve the optimization problem for the transmit powers and BF weight vectors of each user. Furthermore, we derive the analytical expressions for the cumulative density function and the generalized moments of the output signal-to-interference-plus-noise ratios, thereby developing some novel theoretical formulas for the ergodic capacity and the average symbol error rate of each user in the network. Finally, computer simulation results are provided to demonstrate the validity and efficiency of the proposed scheme and its performance analysis.

Symbol Error Analysis of Hybrid Satellite–Terrestrial Cooperative Networks With Cochannel Interference

This letter investigates the effect of cochannel interference (CCI) on a hybrid satellite-terrestrial cooperative relay network (HSTCN), where both the satellite-destination and satellite-relay links undergo the shadowed Rician fading, whereas the relay-destination link follows the Rayleigh fading. By assuming that decode-and-forward (DF) protocol is adopted at the terrestrial relay, and the destination is corrupted by multiple CCI, we first derive the analytical expression for the moment generating function (MGF) of the output signal-to-interference-plus-noise ratio (SINR). Then, based on the Meijer-G functions, we present an approximated yet accurate method to evaluate the average symbol error rate (ASER) of the cooperative network. Moreover, the asymptotic ASER at high signal-to-noise ratio (SNR) with respect to diversity order and array gain are also given to gain further insights. Finally, numerical results are provided to demonstrate the validity of the performance analysis as well as the impact of CCI on the HSTCN.

Secure Transmission in Cognitive Satellite Terrestrial Networks

This paper investigates the physical layer security of a satellite network, whose downlink spectral resource is shared with a terrestrial cellular network. We propose to employ a multi-antenna base station (BS) as a source of green interference to enhance secure transmission in the satellite network. By taking the mutual interference between these two networks into account, we first formulate a constrained optimization problem to maximize the instantaneous rate of the terrestrial user while satisfying the interference probability constraint of the satellite user. Then, with the assumption that imperfect channel state information (CSI) and statistical CSI of the link between the BS and satellite user are available at the BS, we present two beamforming (BF) schemes, namely, hybrid zero-forcing and partial zero-forcing to solve the optimization problem and obtain the BF weight vectors in a closed form. Moreover, we analyze the secrecy performance of primary satellite network by considering two practical scenarios, namely: Scenario I, the eavesdroppers CSI is unknown at the satellite and Scenario II, the eavesdroppers CSI is known at the satellite. Specifically, we derive the analytical expressions for the secrecy outage probability for Scenario I and the average secrecy rate for Scenario II. Finally, numerical results are provided to confirm the superiority of the proposed BF schemes and the validity of the performance analysis, as well as demonstrate the impacts of various parameters on the secrecy performance of the satellite network.

Outage Analysis of Multi-Antenna Cognitive Hybrid Satellite-Terrestrial Relay Networks With Beamforming

This letter investigates the outage performance of a multi-antenna cognitive decode-and-forward (DF) hybrid satellite-terrestrial relay network (HSTRN) with beamforming (BF), where the secondary source and relay can coexist with the primary user (PU) as long as their interference imposed to PU is below a predefined threshold. Specifically, the novel closed-form expression for the outage probability (OP) of the cognitive network are derived. Furthermore, the asymptotic OP expression at high SNR is developed to reveal the diversity order and code gain of the considered network. Finally, simulation results are provided to demonstrate the validity of the theoretical results, and show the effect of antenna number and interfering satellite link on the performance of the cognitive network.

Energy efficient beamforming for secure communication in cognitive radio networks

In this paper, we study the energy efficiency of secure communication in an underlay cognitive radio network (CRN). We first formulate an optimization problem to maximize the secrecy energy efficiency (SEE) while meeting the quality-of-service (QoS) requirement for the primary user and the transmit power constraint at each base station. Since the problem is non-convex and very difficult to solve, we then convert the original fractional form into a subtractive one, and adopt the difference of two-convex functions (D.C.) approximation method to obtain an equivalent convex problem. Furthermore, a two-layer iterative algorithm is presented to solve the problem and obtain the optimal beamforming (BF) weight vectors. Finally, numerical results are provided to demonstrate the superiority of the proposed scheme.

Secure transmission in multi-antenna hybrid satellite-terrestrial relay networks in the presence of eavesdropper

This paper investigates the secrecy capacity of a multi-antenna amplify-and-forward (AF) hybrid satellite-terrestrial relay netwrok (HSTRN), which consists of a satellite, a relay, a terrestrial destination and a terrestrial eavesdropper. Specifically, by employing a two-stage beamforming (BF) scheme, where the relay first adopts the maximal ratio combining (MRC) to receive the signal from satellite and then performs zero-forcing (ZF) to completely null the eavesdroppers signal, the achievable secrecy capacity of the considered hybrid network is derived in closed-from. Eventually, simulation results are provided to demonstrate the superiority of the proposed BF scheme as well as the validity of the theoretical results, and show the effect of various channel parameters on the system performance.

Secrecy Energy Efficiency Maximization in Cognitive Radio Networks

In this paper, we investigate a tradeoff between the secrecy rate (SR) and energy efficiency (EE) in an underlay cognitive radio network that consists of a cognitive base station (CBS), a cognitive user (CU), a primary user (PU), and multiple eavesdroppers (EDs). By using a so-called secrecy EE (SEE), which is defined as the ratio of SR to the total power consumption of CBS, as the design criterion, we formulate an SEE maximization (SEEM) problem for the CBS-CU transmission under the constraints of the transmit power of CBS, the SR of CU, and the quality-of-service (QoS) requirement of PU. Since the formulated optimization problem with a fractional objective function is non-convex and mathematically intractable, we first convert the original fractional objective function into an equivalent subtractive form, and then develop a method of combining the penalty function and the difference of two-convex functions (D.C.) approach to obtain an approximate convex problem. Based on this, an optimal beamforming (OBF) scheme is finally proposed to obtain the optimal solution. Furthermore, to reduce the computational complexity, we design a zero-forcing-based beamforming (ZFBF) scheme to achieve a sub-optimal solution to the SEEM problem. Simulation results are given to illustrate the effectiveness and advantage of the proposed SEE oriented OBF and ZFBF schemes over conventional SR maximization and EE maximization schemes.

Energy efficient optimization for physical layer security in cognitive relay networks

This paper is concerned with the energy efficiency of secure transmission in an underlay cognitive relay network (CRN), where a secondary source communicates with a secondary destination via a multi-antenna relay in the presence of an eavesdropper. We first establish an optimization problem to maximize the secrecy energy efficiency (SEE) under the constraints of data rate and transmit power of the cognitive transmission as well as the interference limitation to the primary user. Then, we recast the original non-convex problem in fractional form into an equivalent subtractive one with an additional rank-one constraint. Moreover, we incorporate the rank-one constraint into the objective function as the penalty term and apply the difference of two-convex functions (D.C.) approach to obtain an equivalent convex problem. Finally, we present an iterative algorithm to obtain the optimal solution for the SEE maximization problem in the CRN. Numerical results are provided to demonstrate the effectiveness of the proposed scheme.

Performance Analysis of Hybrid Satellite---Terrestrial Cooperative Systems with Fixed Gain Relaying

In this paper, we investigate the performance of a hybrid satellite–terrestrial cooperative relay system, where both of the source-relay and source–destination links experience independent non-identical shadowed-Rician fading while the relay-destination link undergoes uncorrelated Rayleigh fading. By employing maximal-ratio-combining at the destination to combine the signals from the direct link and the fixed-gain relay links, we first obtain the analytical expression for the moment generating function (MGF) of the output signal-to-noise ratio (SNR). Then, with the help of the obtained MGF, we derive the theoretical formulas for the ergodic capacity and average symbol error rate of the considered system. Moreover, the asymptotic analysis at high SNR is also presented to reveal the diversity order and array gain of the system. Finally, the effectiveness of the analytical results is verified through comparison with Monte Carlo simulations.

Effect of imperfect channel state information and co-channel interferences on two-hop fixed gain amplify-and-forward relay networks with beamforming

This letter investigates the joint effects of imperfect channel state information and co-channel interferences on a two-hop fixed gain amplify-and-forward AF relay network with beamforming. Specifically, the analytical expressions of the outage probability and the average symbol error rate for the AF relaying are derived. Moreover, the asymptotic analysis at high signal-to-noise ratio is also presented to reveal the diversity order and array gain of the considered AF relay system. Finally, computer simulations are given to confirm the validity of the analytical results. Copyright