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

MinChul Ju,Kyu-Min Kang,Kyu-Sung Hwang,Cheol Jeong IEEE 2015 IEEE journal on selected areas in communications Vol.33 No.12

<P>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.</P>

Joint Relay Selection and Relay Ordering for DF-Based Cooperative Relay Networks

MinChul Ju,Il-Min Kim,Dong In Kim IEEE 2012 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.60 No.4

<P>Relay selection (RS) has widely been studied for both decode-and-forward (DF) and amplify-and-forward (AF) protocols, and relay ordering (RO) was recently proposed for the AF protocol only . The two strategies, RS and RO, have been individually shown to be very effective to enhance the performance of cooperative relay networks. In this letter, we first discuss the fundamental difference of the two schemes and investigate an important tradeoff in terms of spectral efficiency and energy efficiency between RS and RO. Specifically, RS is more spectrally efficient, whereas RO can be more efficient in energy consumption. Then we demonstrate that indeed RS and RO generally have different outage performance and may complement each other depending on channel conditions. To optimize the outage performance, therefore, we combine the two strategies, RS and RO, and we propose joint RS-RO, followed by exact outage probability derivation of the joint RS-RO in closed-form. Finally, we obtain some interesting insights into the issue of selecting efficient transmission schemes between RS and RO.</P>

Error Performance Analysis of BPSK Modulation in Physical-Layer Network-Coded Bidirectional Relay Networks

MinChul Ju,Il-Min Kim IEEE 2010 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.58 No.10

<P>We analyze the error performance of the physical-layer network coding (PNC) protocol without channel coding in bidirectional relay networks for binary phase shift keying (BPSK) over Rayleigh fading channels. It is assumed that a bidirectional relay network consists of two sources and a relay, where each node has a single antenna and operates in a half-duplex mode, and the PNC over finite GF(2) is employed. In this system, since the maximum-likelihood (ML) detection metric of the multiple access channel (MAC) at the relay is given by the sum of two exponential functions, it is not possible to utilize the classical Euclidean distance rule. To make the performance analysis tractable, we approximate the ML detection metric by adopting the max-log approximation. Then we derive tight upper and lower bounds in closed form for the average symbol error probability of the MAC at the relay. Finally, we obtain tight upper and lower bounds in closed form for the end-to-end average bit-error rate (BER).</P>

Cognitive Radio Networks With Secondary Network Selection

MinChul Ju,Kyu-Min Kang IEEE 2016 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.65 No.2

<P>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.</P>

Opportunistic Transmission of Nonregenerative Network With Untrusted Relay

MinChul Ju,Do-Hoon Kim,Kyu-Sung Hwang IEEE 2015 IEEE Transactions on Vehicular Technology VT Vol.64 No.6

<P>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.</P>

Joint Relay Selection and Opportunistic Source Selection in Bidirectional Cooperative Diversity Networks

MinChul Ju,Il-Min Kim IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.6

<P>Relay selection (RS) has widely been studied in the literature, and an opportunistic source selection (OSS) protocol with a single relay has recently been proposed. Since RS and OSS could individually improve the performance of cooperative diversity networks, optimum combining of RS and OSS is an interesting topic. In this paper, we optimally combine RS and OSS in the sense that the mutual information is maximized, and we propose a joint RS-OSS protocol in an amplify-and-forward (AF)-based bidirectional cooperative diversity network, which consists of two different end-sources and multiple relays. In this network, a best source is selected to transmit data to the other source with the help of a selected best relay in an opportunistic manner, depending on channel conditions. Then, to show the performance of the joint RS-OSS, we derive the outage probability and the average bit error rate (BER) for <I>M</I>-quadrature amplitude modulation (QAM). Numerical results confirm that the derived outage probability and the average BER expressions are very accurate. In addition, we find that the proposed joint RS-OSS considerably outperforms both RS and OSS in terms of outage probability and average BER and that the performance is highly dependent on relay location. The obtained outage probability and average BER will help the design of reliable bidirectional cooperative diversity networks in determining the system parameters, such as relay location, and the transmission power at source and relay.</P>

ML performance analysis of the decode-and-forward protocol in cooperative diversity networks

Minchul Ju,Il-Min Kim IEEE 2009 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.8 No.7

<P>We analyze the maximum-likelihood (ML) performance of the decode-and-forward protocol in a cooperative diversity network which consists of a source, a relay, and a destination with a direct path signal, but which is not equipped with cyclicredundancy- check (CRC) codes. In this system, due to a symbol error at the relay, the ML receiver at the destination needs to consider all the possible symbol detection scenarios at the relay as well as at the destination. Therefore, the ML detection metric is given by a linear combination of exponential functions, which prevents the use of the classical minimum Euclidean distance rule. Adopting the max-log approximation, we approximate the ML detection rule which makes the ML performance analysis tractable. In order to facilitate the derivation of decision regions, we simplify the ML detection rule in the two-dimensional real space such that two metric values of two adjacent constellation points are sequentially compared. Then we obtain decision regions in a form without union and intersection. Finally, based on the decision regions, we derive a very accurate closedform BER approximation for M-pulse amplitude modulation (PAM) and M-quadrature amplitude modulation (QAM). The obtained BER expression can serve as the error performance upper-bound of the decode-and-forward protocol in cooperative diversity networks.</P>

Opportunistic Source/Destination Cooperation in Cooperative Diversity Networks

MinChul Ju,Il-Min Kim,Dong In Kim IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.12

<P>In this paper, we combine opportunistic transmission and source/destination cooperation in a decode-and-forward (DF)-based two-hop cooperative diversity network consisting of multiple source-destination pairs and a single relay. Firstly, we consider a special scenario with two source-destination pairs. For this network, there are two possible strategies in each hop: no-cooperation or cooperation. Considering the combination of the two strategies in two cascaded hops, we investigate four different end-to-end transmission strategies, and we find that the four strategies complement one another depending on channel conditions in terms of outage performance. To maximize the mutual information, we propose an optimum joint selection of source-destination pair and end-to-end transmission strategy. Then we show that the optimum joint selection scheme can be simplified without loss of outage performance, and derive its exact outage probability in closed-form. Secondly, we generalize the proposed transmission strategy into a scenario with multiple source-destination pairs. For this network, we first propose an optimum end-to-end transmission strategy to maximize the mutual information, then a suboptimum end-to-end transmission strategy to reduce the signaling overhead and computational complexity. For the suboptimum strategy, we derive the outage probability and diversity order.</P>

Outage Equivalence of Opportunistic Relaying and Selection Cooperation in Presence of Co-Channel Interference

MinChul Ju,Kyu-Sung Hwang IEEE 2015 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.14 No.6

<P>In this paper, we investigate two different relay selection schemes, opportunistic relaying (OR) and selection cooperation (SC), for decode-and-forward (DF)-based relay networks consisting of a source, multiple relays, and a destination in the presence of multiple co-channel interferers, where each terminal has a single antenna and operates in a half-duplex mode. For the network, we first extend the conventional OR and SC to relay networks with the direct-path and multiple co-channel interferers, and obtain the exact and closed-form outage probability of the OR. Then, we show that the SC is equivalent to the OR in terms of outage performance for relay networks with the direct-path and multiple co-channel interferers. Finally, we show that the SC and OR are outage-optimal under the aggregate power consumption constraint at the relays for relay networks with the direct-path and multiple co-channel interferers.</P>

도청자가 존재하는 무선 협력 네트워크의 전달 단말 선택을 통한 보안 전송률 최대 전송기술 및 성능분석

주민철(MinChul Ju),권대길(Tai-Gil Kwon),조진웅(Jin-Woong Cho) 한국멀티미디어학회 2015 멀티미디어학회논문지 Vol.18 No.4