• 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.

• 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.

• 한국통신학회논문지
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• 제40권3호
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• pp.451-458
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• 2015

무선랜 이용률 증가에 따라 무선랜 단말뿐만 아니라 AP의 밀집도가 증가하고 있고, 이로 인해 무선랜의 실제 성능(real performance)이 저하되고 있다. 이를 개선하기 위한 PHY/MAC 기술 중 OFDMA와 full duplex가 있다. 기존 OFDMA기반 무선랜 MAC 연구는 채널 utilization과 충돌확률 측면에서의 문제점이 있고 따라서 보다 효율적인 채널할당 프로토콜에 대한 연구가 필요하다. Full duplex는 같은 주파수에 동시에 송수신이 가능한 방식으로 half duplex에 비해 더 유연한 채널할당이 가능하다. 본 논문에서는 full duplex 전송 노드의 idle 채널정보를 바탕으로 서브 채널을 할당하는 OFDMA FD-MAC(Full Duplex MAC) 프로토콜을 제안하였다. 또한, 성능분석을 통해 throughput이 개선됨을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.3000-3022
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• 2019

Full-duplex (FD) technologies enable wireless nodes to simultaneously transmit and receive signal using the same frequency-band. The FD modes could improve their physical layer throughputs. However, in the wireless ad hoc networks, the FD communications also produce new interference risks. On the one hand, the interference ranges (IRs) of the nodes are enlarged when they work in the FD mode. On the other hand, for each FD pair, the FD communication may cause the potential hidden terminal problems to appear around the both sides. In this paper, to avoid the interference risks, we first model the IR of each node when it works in the FD mode, and then analyze the conditions to be satisfied among the transmission ranges (TRs), carrier-sensing ranges (CSRs), and IRs of the FD pair. Furthermore, in the media access control (MAC) layer, we propose a specific method and protocol for collision avoidance. Based on the modified Omnet++ simulator, we conduct the simulations to validate and evaluate the proposed FD MAC protocol, showing that it can reduce the collisions effectively. When the hidden terminal problem is serious, compared with the existing typical FD MAC protocol, our protocol can increase the system throughput by 80%~90%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권10호
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• pp.3887-3907
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• 2015

This paper introduces a full duplex single secondary user multiple-input multiple-output (FD-SSU-MIMO) cognitive radio network, where secondary user (SU) opportunistically accesses the authorized spectrum unoccupied by primary user (PU) and transmits data based on FD-MIMO mode. Then we study the network achievable average sum-rate maximization problem under sum transmit power budget constraint at SU communication nodes. In order to solve the trade-off problem between SU's sensing time and data transmission time based on opportunistic spectrum access (OSA) and the power allocation problem based on FD-MIMO transmit mode, we propose a simple trisection algorithm to obtain the optimal sensing time and apply an alternating optimization (AO) algorithm to tackle the FD-MIMO based network achievable sum-rate maximization problem. Simulation results show that our proposed sensing time optimization and AO-based optimal power allocation strategies obtain a higher achievable average sum-rate than sequential convex approximations for matrix-variable programming (SCAMP)-based power allocation for the FD transmission mode, as well as equal power allocation for the half duplex (HD) transmission mode.

• 한국통신학회논문지
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• 제35권6A호
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• pp.568-576
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• 2010

본 논문은 복호 후 전달 (decode-and-forward, DF) 프로토콜 하에서 전이중 통신방식 릴레이 (full duplex relay, FDR) 의 오수신 확률 (outage probability) 성능을 페이딩 채널하에서 유도하였다. 준기지국 형태의 고정된 릴레이를 가정하여 송신단과 릴레이 사이의 채널은 LOS (line of sight) 전파가 존재하는 Rician 채널을, 다른 링크 채널은 Rayleigh 채널을 고려하였다. 또한, 이 분석을 통해 전이중 통신 (full duplex, FD)으로 인한 간섭 문제와 자원의 효율성 향상 측면을 고려하여 실제적으로 FDR이 반이중 통신방식 릴레이 (half duplex relay, HDR) 보다 낮은 오수신 확률 성능을 가지기 위한 조건을 제시하였다. 분석된 오수신 확률 성능의 정확성은 모의 실험을 통하여 검증되었다.

• 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.

• 한국통신학회논문지
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• 제40권12호
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• pp.2389-2391
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• 2015

본 논문은 전 이중 다중 안테나 셀룰라 네트워크에서 간섭 정렬 타당성을 다루고 있다. 간섭 정렬을 위한 필요충분조건 정립과, 달성 가능 합 자유도를 대칭 네트워크에 내에서 설명했다. 실험결과 기존 반 이중 통신의 합 자유도 보다 향상 되는 것을 확인 할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권11호
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• pp.5338-5359
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• 2017

In-band full-duplex (IBFD) wireless communication supports symmetric dual transmission between two nodes and asymmetric dual transmission among three nodes, which allows improved throughput for distributed IBFD wireless networks. However, inter-node interference (INI) can affect desired packet reception in the downlink of three-node topology. The current Half-duplex (HD) medium access control (MAC) mechanism RTS/CTS is unable to establish an asymmetric dual link and consequently to suppress INI. In this paper, we propose a medium access control mechanism for use in distributed IBFD wireless networks, FD-DMAC (Full-Duplex Distributed MAC). In this approach, communication nodes only require single channel access to establish symmetric or asymmetric dual link, and we fully consider the two transmission modes of asymmetric dual link. Through FD-DMAC medium access, the neighbors of communication nodes can clearly know network transmission status, which will provide other opportunities of asymmetric IBFD dual communication and solve hidden node problem. Additionally, we leverage FD-DMAC to transmit received power information. This approach can assist communication nodes to adjust transmit powers and suppress INI. Finally, we give a theoretical analysis of network performance using a discrete-time Markov model. The numerical results show that FD-DMAC achieves a significant improvement over RTS/CTS in terms of throughput and delay.

• 한국통신학회논문지
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• 제41권11호
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• pp.1374-1379
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• 2016

이제까지의 협력 인지 통신망에서는 쓰는 이들이 거의 대부분 서로 반 이중 방식으로 신호를 주고 받았다. 이 논문에서는 부 쓰는이들이 전 이중 통신 기술을 쓰는 협력 인지 통신망을 제안하고 그 성능을 간단히 살펴본다. 제안한 방식에서는 협력 인지 통신망의 부 쓰는이들이 동시 송수신 안테나를 쓰는 환경을 생각하여, 전 이중으로 통신할 수 있도록 하였다. 제안한 방식에서 이룰 수 있는 전송률을 해석적으로 얻고, 이제까지의 협력 인지 통신망보다 전송률 성능이 더 높다는 것을 수치적인 계산으로 보인다.