MinChul Ju

Maximum Transmission Rate of PSR/TSR Protocols in Wireless Energy Harvesting DF-Based Relay Networks

In this paper, we consider the power splitting relaying (PSR) and time switching relaying (TSR) protocols for decode-and-forward (DF)-based relay networks consisting of a source, a relay, and a destination. For the networks, the relay is assumed to have a rechargeable battery with a certain amount of remaining energy for energy harvesting through the received signal transmitted from the source. Specifically, for the PSR protocol with and without the direct-path, we present the outage probability expression with a given power splitting coefficient, and we obtain the optimum power splitting coefficient to maximize the transmission rate and derive its transmission rate and outage probability, where the optimum coefficient depends on channel conditions and remaining energy. For the TSR protocol with and without the direct-path, we present the outage probability expression with a given time switching coefficient, and we obtain the optimum time switching coefficient to maximize the transmission rate and derive its transmission rate, where the optimum coefficient also depends on channel conditions and remaining energy.

Outage Performance of Opportunistic Two-Way Amplify-and-Forward Relaying with Outdated Channel State Information

In this paper, we study the outage performance of an amplify-and-forward (AF)-based two-way relaying (TWR) system with multiple relays where a single relay selection is performed based on outdated channel state information (CSI). Specifically, we propose a single relay selection scheme in AF-based TWR system under outdated CSI conditions. With this policy, we offer a statistical analysis of the signal-to-noise ratio per hop and analyze the outage probability with asymmetric outage thresholds based on CSI-assisted AF protocol. Additionally, we provide the exact and asymptotic expressions based on the provided statistical/joint statistical analyses of a dual-hop AF transmission. Finally, we verify our analytical results with some selected computer-based simulation results.

Opportunistic Transmission of Nonregenerative Network With Untrusted Relay

In this paper, we consider an opportunistic transmission scheme of nonregenerative relay networks consisting of a source, a destination, and an untrusted relay, where the relay has a different security clearance from the source-destination pair. In this network, the information is transmitted through the direct link if the secrecy rate of the direct link is larger than or equal to that of the triangular link, and the information is transmitted through the triangular link if the secrecy rate of the direct link is smaller than that of the triangular link. For the network, we derive the exact secrecy outage probability in integral form and its closed-form lower bound. When the required secrecy rate is larger than a certain threshold value (0.6942 b/s/Hz), we show that the help of the untrusted relay is unnecessary if the source broadcasts the information and the half-duplex mode is considered.

Relay Selection of Cooperative Diversity Networks With Interference-Limited Destination

We study relay selection in both decode-and-forward (DF)-based and amplify-and-forward (AF)-based cooperative diversity networks consisting of a source, multiple relays, and a destination in the presence of multiple interferers, where each terminal has a single antenna and operates in half-duplex mode. In the network, it is assumed that the multiple interferers locate near the destination and far away from relays; thus, only the destination receives interfering signals, which is referred to as the interference-limited destination. Specifically, we first propose relay selection to maximize the mutual information on cooperative networks with the interference-limited destination. Then, for relay selection of DF-based networks, we derive the exact outage probability. Finally, for relay selection of AF-based networks, we derive the exact outage probability in integral form and its closed-form lower bound.

Visible light communications with color and dimming control by employing VPPM coding

We propose a data transmission scheme using visible light LEDs with color and dimming control. PWM and VPPM coding schemes are used for the control of color and dimming, respectively. The coding procedures and the test results are provided.

Optimal Training Signal Design for Estimation of Correlated MIMO Channels in Two-Way Amplify-and-Forward Relay Systems

In this study, we design a training signal for a correlated two-way amplify-and-forward (AF) relay channel, where the relay system consists of two sources and one relay, and each terminal is equipped with multiple antennas. In the system, given that a mean square error (MSE) exists at each source, we minimize the sum of the two MSEs. In particular, we first derive a linear minimum MSE channel estimator with an arbitrary training signal. Second, we formulate the training signal design problem to minimize the sum of the MSEs of the two sources. Finally, we present the optimal structure of the training signal. The optimal training signal is obtained numerically, and a suboptimal training signal is obtained in a closed form. The simulation results show that the MSE performance of the closed-form training signal is almost the same as that of the optimal training signal.

Secrecy outage probability of amplify-and-forward transmission with multi-antenna relay in presence of eavesdropper

In this letter, we offer the secrecy outage probability of the amplify-and-forward (AF) transmission, which consists of one source, one destination, one relay, and one passive eavesdropper. Particularly, we consider that the relay is equipped with multiple antennas while other terminals is utilized with single antenna and apply some diversity techniques (for both the reception and the transmission) in the relay to achieve gains in a secrecy outage performance. Additionally, we analyze the exact secrecy outage probability of the proposed systems in a one-integral form. Finally, some numerical examples are given to verify our provided analytical results for different system conditions.

On the outage performance of two-way amplify-and-forward relaying with outdated CSI over multiple relay network

Two-way relaying (TWR) has recently received a great deal of attention since it can recover the loss in spectral efficiency that characterizes conventional half-duplex transmission systems operating within cooperative networks. Additionally, when relay selection is considered in multiple relay network, outdated channel state information (CSI) due to feedback delays can create important challenges from a practical point of view. In this paper, we study the outage performance of an amplify-and-forward (AF)-based TWR system with multiple relays where a single relay selection is performed based on outdated CSI. Specifically, we consider a single relay selection scheme in AF-based TWR system under outdated CSI conditions and offer a statistical analysis of the signal-to-noise ratio per hop with the given policy. For the analysis of the outage probability with asymmetric outage thresholds, we offer an accurate closed-form approximation based on the provided statistical/joint statistical analyses of a dual-hop AF transmission. Finally, we verify our analytical results with some selected computer-based simulation results.

Bi-directional visible light communication using performance-based selection of IR-LEDs in upstream transmission

In this paper, we propose a novel upstream transmission scheme in bi-directional visible light communication system, which consists of multiple narrow beam infrared light emitting diodes (IR-LEDs). Specifically, we select the best IR-LED among multiple IR-LEDs. The condition and algorithms of selection are provided. A small test-bed is implemented and its results are provided.

Cognitive Radio Networks With Secondary Network Selection

In this paper, we study cognitive radio (CR) networks that consist of multiple secondary TV band device (TVBD) station-user pairs and one primary digital TV (DTV) station-user pair, where each terminal has a single antenna. Specifically, we consider spectrum sharing (SS)-based secondary TVBD networks to effectively utilize limited spectrum resources in the presence of cochannel primary DTV interference. We first present an opportunistic single secondary network selection scheme to maximize the mutual information over all secondary TVBD networks under the constraint of the availability of the primary DTV service. Then, the performance bound of CR networks with the secondary network selection is obtained through the derivation of an exact and closed-form outage probability. It is shown that the derived outage probability is given as a function of transmission power, channel coefficients, and target rates of both the primary DTV network and the secondary TVBD networks.