• ETRI Journal
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• 제42권1호
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• pp.17-25
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• 2020

Multiple-input multiple-output systems can achieve a full sum rate (SR) via full duplex (FD). However, its performance is degraded by self-interference (SI) that occurs between the transmitter and receiver at the same node and thus is constrained by error floors. Conversely, half duplex (HD) can avoid the SI albeit at lower spectral efficiency, and the slope of its error curve is determined by the diversity order. In this study, a link selection scheme based on switching between FD and HD is examined as a simple method to improve the bit error rate (BER) performance of FD systems. In the proposed link selection algorithm, either FD or HD is selected based on the received minimum distance and signal-to-interference plus noise ratio. Simulation results indicate that the proposed hybrid FD/HD switching system offers significant BER performance improvement when compared with that of the conventional FD and FD based on only the received minimum distance under the same fixed SR. Under relatively sufficient SI cancellation, it is demonstrated to outperform the HD with a diversity advantage in low and medium signal-to-noise ratio region.

• 한국통신학회논문지
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• 제38A권5호
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• pp.436-442
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• 2013

본 논문에서는 두 개 이상의 안테나를 사용하는 소스 노드, 두 개의 안테나를 사용하는 릴레이 노드, 두 개의 안테나를 사용하는 목적지 노드로 구성된 특별한 경우의 half-duplex (HD) dynamic decode and forward (DDF) 릴레이 프로토콜에 대한 diversity multiplexing tradeoff (DMT) 함수를 유도하였다. 본 논문에서 유도한 프로토콜의 DMT 함수를 동일한 안테나 개수를 사용하는 노드들로 구성된 HD NAF 프로토콜에 대한 DMT 함수와 비교하였으며, 더불어 두 개의 안테나를 사용하는 소스 노드, 두 개 이상의 안테나를 사용하는 릴레이 노드, 두 개의 안테나를 사용하는 목적지 노드로 구성된 HD DDF 릴레이 프로토콜에 대한 DMT 함수와 비교하였다.

• 한국통신학회논문지
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• 제38A권5호
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• pp.426-435
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• 2013

소스 노드, 목적지 노드, 릴레이 노드 중 하나의 노드에서 다중 안테나를 사용하는 특별한 세 가지 경우의 half-duplex (HD) dynamic decode and forward (DDF) 릴레이 프로토콜들에 대한 diversity multiplexing tradeoff(DMT) 함수를 유도하였다. 이 세 가지 릴레이 프로토콜들의 DMT 함수들을 상호 비교하였으며 nonorthogonal amplify-and-forward (NAF) 프로토콜들의 DMT 함수와 비교하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1311-1324
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• 2019

In the traditional cellular network communication, the cellular user and the base station exchange information through the uplink channel and downlink channel. Meanwhile, device-to-device (D2D) users access the cellular network by reusing the channel resources of the cellular users. However, when cellular user channel conditions are poor, not only D2D user cannot reuse its channel resources to access the network, but also cellular user's communication needs cannot be met. To solve this problem, we introduced a novelty D2D communication mechanism in the downlink, which D2D transmitter users as half-duplex (HD) relays to assist the downlink transmission of cellular users with reusing corresponding spectrum. The optimization goal of the system is to make the cellular users in the bad channel state meet the minimum transmission rate requirement and at the same time maximize the throughput of the D2D users. In addition, i for the purpose of improving the efficiency of relay transmission, we use two-antenna architecture of D2D relay to enable receive and transmit signals at the same time. Then we optimized power of base station and D2D relay separately with consideration of backhaul interference caused by two-antenna architectures. The simulation results show that the proposed HD relay strategyis superior to existing HD and full-duplex (FD) models in the aspects of system throughput and power efficiency.

• ETRI Journal
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• 제40권2호
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• pp.207-217
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• 2018

As implementation of the in-band full duplex (IFD) transceiver becomes feasible, research interest is growing with respect to using IFD communication with cellular networks. However, the cellular network in which the IFD communication is applied inevitably suffers from an increase of the co-channel interference (CCI) due to IFD simultaneous transmission and reception. In this paper, we analyze the performance of a cellular network based on uni-directional IFD (UD-IFD) communication, wherein an IFD base station simultaneously supports downlink and uplink transmissions of half-duplex (HD) users. In addition, a multi-pair CCI cancellation (MP-CCIC) method combining CCIC and user pairing is proposed to improve the performance of the UD-IFD network. Simulation results showed that, compared to a conventional HD cellular network without using CCIC, capacity gain was not obtained in the UD-IFD cellular network. On the other hand, when applying the proposed MP-CCIC, the capacity of the UD-IFD cellular network greatly improved compared to that of an HD cellular network.

• ETRI Journal
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• 제39권6호
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• pp.794-802
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• 2017

In this paper, a wireless powered communication network (WPCN) consisting of a hybrid access point (H-AP) and multiple user equipment (UE), all of which operate in full-duplex (FD), is described. We first propose a transceiver structure that enables FD operation of each UE to simultaneously receive energy in the downlink (DL) and transmit information in the uplink (UL). We then provide an energy usage model in the proposed UE transceiver that accounts for the energy leakage from the transmit chain to the receive chain. It is shown that the throughput of an FD WPCN using the proposed FD UE (FD-WPCN-FD) can be maximized by optimal allocation of the UL transmission time to the UE by solving a convex optimization problem. Simulation results reveal that the use of the proposed FD UE efficiently improves the throughput of a WPCN with a practical self-interference cancellation capability at the H-AP. Compared to the WPCN with FD H-AP and half-duplex (HD) UE, FD-WPCN-FD achieved an 18% throughput gain. In addition, the throughput of FD-WPCN-FD was shown to be 25% greater than that of WPCN in which an H-AP and UE operated in HD.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3908-3920
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• 2015

In this paper, performance analysis of full-duplex (FD) relay selection under decode-and-forward (DF) relaying mode is carried out by taking into account several critical factors, including the distributions of the received signal-to-noise ratio (SNR) and the outage probability of wireless links. The tradeoff between the FD and half-duplex (HD) modes for relay selection techniques is also analyzed, where the former suffers from the impact of residual self-interference, but the latter requires more channel resources than the former (i.e., two orthogonal channels are required). Furthermore, the impact of optimal power allocation (OPA) on the proposed relay-selection scheme is analyzed. Particularly, the exact closed-form expressions for outage probability of the proposed scheme over Rayleigh fading channels are derived, followed by validating the proposed analysis using simulation. Numerical results show that the proposed FD based scheme outperforms the HD based scheme by more than 4 dB in terms of coding gain, provided that the residual self-interference level in the FD mode can be substantially suppressed to the level that is below the noise power.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3131-3149
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• 2016

In-band Full-duplex (IBFD) wireless communication allows improved throughput for wireless networks. The current Half-duplex (HD) medium access mechanism Request to Send/Clear to Send (RTS/CTS) has been directly applied to IBFD wireless networks. However, this is only able to support a symmetric dual link, and does not provide the full advantages of IBFD. To increase network throughput in a superior way to the HD mechanism, a novel three-way handshaking access mechanism RTS/SRTS (Second Request to Send)/CTS is proposed for point to multipoint (PMP) IBFD wireless networks, which can support both symmetric dual link and asymmetric dual link communication. In this approach, IBFD wireless communication only requires one channel access for two-way simultaneous packet transmissions. We first describe the RTS/SRTS/CTS mechanism and the symmetric/asymmetric dual link transmission procedure and then provide a theoretical analysis of network throughput and delay using a Markov model. Using simulations, we demonstrate that the RTS/SRTS/CTS access mechanism shows improved performance relative to that of the RTS/CTS HD access mechanism.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.583-585
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• 2016

The recent advances in wireless networks area have led to new techniques, such as small cells or full-duplex (FD) transmission, have also been developed to further increase the network capacity. Particularly, full-duplex communication promises expected throughput gain by doubling the spectrum compared to half-duplex (HD) communication. Because this technique permits one set of frequencies to simultaneously transmit and receive signals. In this paper, we focus on the binary power control for the users and the base stations in full-duplex multiple cellulars wireless networks to obtain optimal sum-rate under the effect interference and noise. We investigate with a scenario in there one carrier is assigned to only one user in each cell and construct a model for this problem. In this work, we apply the binary power control by the its simplification in the implemented algorithm for both uplink and downlink simultaneously to maximize sum data rate of the system. At first, we realize the 2-cells case separately to check the optimal power allocation whether being binary. Then, we carry on with N-cells case in general through properties of binary power control.

• 한국통신학회논문지
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• 제35권12C호
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• pp.1020-1028
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• 2010

릴레이는 차세대 이동통신 시스템에서 기지국의 서비스 커버리지 영역을 확대하고 음영지역을 해소하기 위해 반드시 필요한 기술이다. 하지만, 기존의 릴레이 관련 연구는 주로 반이중 모드, 즉 서로 다른 시간 혹은 주파수에서 송수신을 수행하도록 제한하고 있다. 반이중 릴레이는 구현이 쉬운 반면 릴레이 송수신 지원 구분이 필요하기 때문에 전체 시스템 용량이 줄어드는 단점이 있다. 본 논문에서는 다중 안테나를 갖는 전이중 릴레이의 다중 사용자 precoding 및 sum rate 정합 기반의 전력 할당 방식을 제안한다. 전이중 릴레이는 같은 주파수에서 동시에 송수신을 수행하기 때문에 릴레이의 송수신 안테나 사이에 발생하는 자기 간섭 문제를 해결해야 한다. 본 논문에서 제안하는 precoding 기법을 통해 다중 사용자 MIMO 전송이 가능하면서 동시에 전이중 릴레이의 자기 간섭을 제거할 수 있다. 또한, 릴레이가 기지국으로부터 수신하는 정보량과 단말국으로 전달하는 정보량이 동일하도록 하는 조건 하에서 전체 시스템 용량을 최대화하는 전력 할당 기법을 제안한다.