• 한국정보통신학회논문지
• /
• 제20권8호
• /
• pp.1438-1443
• /
• 2016

본 논문에서는 양방향 중계 채널에서 중계기에 다중안테나가 존재할 경우 물리계층 네트워크 코딩 기법의 성능분석을 수행하였다. 2개의 소스 노드는 하나의 안테나를 가진다고 가정하고 중계기에는 다중안테나가 설치되었다고 가정한다. 본 논문에서는 소스 노드와 중계노드에 각각 하나의 안테나가 존재하는 기존 시스템을 중계기에 다중안테나가 존재하는 환경으로 확장한다. 특히, 중계기에서 2개의 소스 노드들로부터 도착한 패킷을 복호하는 과정에서 각 패캣을 복호한 후 네트워크 부호화를 수행하는 개별복호기술과 소스 노드들로부터 도착한 2개의 패킷을 동시에 고려하여 직접복호하는 기술을 비교분석한다. 다중안테나기반의 중계기를 사용할 경우 물리계층 네트워크 코딩의 비트오류성능이 중계기의 안테나의 개수가 증가함에 따라 향상되는 것을 확인하였다.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2010년도 추계학술대회
• /
• pp.465-467
• /
• 2010

This paper proposes MIMO two-way cooperative relay scheme to optimize the end to end capacity in wireless multi-hop mesh network. The basic idea is to perform data transmission via multi-hop relay nodes, in equidistant topology, this method is quite efficient. However, on one hand this topology is very rare in practical situation, on the other hand, in real practical situation where the topology is most likely non equidistant, the end to end capacity significantly degrades due to bottleneck link caused by uneven SNR. Moreover, the end to end capacity degrades at high SNR due to overreach interference from far nodes existing in multi-hop relay networks. In this paper, MIMO two-way cooperative relay in the region of non equidistant nodes is found efficient to improve the end to end capacity. The proposed scheme is validated using numerical simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권12호
• /
• pp.5361-5374
• /
• 2016

Combining channel coding and network coding in a physical layer in a fading channel, generalized joint channel-network coding (G-JCNC) is proved to highly perform in a two-way relay channel (TWRC). However, most relevant discussions are restricted to symmetric networks. This paper investigates the G-JCNC protocols in an asymmetric TWRC (A-TWRC). A newly designed encoder used by source nodes that is dedicated to correlate codewords with different orders is presented. Moreover, the capability of a simple common non-binary decoder at a relay node is verified. The effects of a power match under various numbers of iteration and code lengths are also analyzed. The simulation results give the optimum power match ratio and demonstrate that the designed scheme based on G-JCNC in an A-TWRC has excellent bit error rate performance under an appropriate power match ratio.

• 방송공학회논문지
• /
• 제21권1호
• /
• pp.109-112
• /
• 2016

본 논문에서는 다수의 간섭자로부터의 간섭 신호가 존재할 때 양방향 중계 네트워크의 불능 확률을 분석하였다. 양방향 중계 네트워크에서 한사용자는 다른 선택된 사용자와 세 단계로 통신한다. 제안된 네트워크에서 사용자 선택 기준을 제시하였으며 불능 확률을 수식적으로 유도하였다. 컴퓨터 모의 실험을 통해 제안된 분석과 모의실험이 잘 일치함을 확인하였으며 유저 수와 간섭자의 수의 불능 확률에의 영향을 보였다.

• Journal of Communications and Networks
• /
• 제16권1호
• /
• pp.45-55
• /
• 2014

The paper investigates the problem of designing the multiple-antenna relay in a two-way relay network by taking into account the imperfect channel state information (CSI). The objective is to design the multiple-antenna relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. In particular, the worst-case transmit power at the multiple-antenna relay is minimized while guaranteeing the worst-case quality of service requirements that the received signal-to-noise ratio (SNR) at both sources are above a prescribed threshold value. Since the worst-case received SNR expression is too complex for subsequent derivation and processing, its lower bound is explored instead by minimizing the numerator and maximizing the denominator of the worst-case SNR. The aforementioned problem is mathematically formulated and shown to be nonconvex. This motivates the pursuit of semidefinite relaxation coupled with a randomization technique to obtain computationally efficient high-quality approximate solutions. This paper has shown that the original optimization problem can be reformulated and then relaxed to a convex problem that can be solved by utilizing suitable randomization loop. Numerical results compare the proposed multiple-antenna relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. Finally, the feasibility of the proposed design and the associated influencing factors are discussed by means of extensive Monte Carlo simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권2호
• /
• pp.566-578
• /
• 2018

In this paper, we design a segment training based individual channel estimation (STICE) scheme for the classical two-way relay network (TWRN) with multi-pair sources (MPS) and amplify-and-forward (AF). We adopt the linear minimum mean square error (LMMSE) channel estimator to minimize the mean square error (MSE) without channel estimation error, where the optimal power allocation strategy from the relay for different sources is obtained. Then the MSE gains are given with different source pairs among the proposed power allocation scheme and the existing power allocation schemes. Numerical results show that the proposed method outperforms the existing ones.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제8권10호
• /
• pp.3409-3422
• /
• 2014

The frequency spectrum available for the wireless communication is extremely crowded. In order to improve the spectral efficiency, the two-way relay networks have aroused great attention. A simple $N^{th}$ best-relay selection criterion for the opportunistic two-way relay networks is proposed, which can be implemented easily by extending the distributed timer technique in practice, since the proposed criterion is mainly based on the channel gains. The outage performance of the proposed relay selection scheme is analyzed under the outdated channel state information (CSI), and a tight closed-form lower bound and asymptotic value of the outage probability over Rayleigh fading channels are obtained. Simulation results demonstrate that the tight closed-form lower bound of the outage probability very closely matches with simulated ones in the whole SNR region, and the asymptotic results provide good tight approximations to the simulation ones, especially in the high SNR region.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제6권9호
• /
• pp.2098-2117
• /
• 2012

This paper jointly investigates the bandwidth allocation, transmission strategy and relay positions for two-way transmission aware cellular networks with network coding (NC). Our goal is to minimize the transmission power of mobile terminals (MTs). Consider a cellular system, where multiple MTs exchange information with their common base station, firstly, we propose an efficient bandwidth allocation method and then give a transmission strategy for each MT to determine whether to use relay stations (RSs) for its two-way transmission with the BS or not. To further improve the system performance, the optimal positions of RSs are also jointly discussed. A GA-based algorithm is presented to obtain the optimum positions for RSs. Besides, the impacts of frequency reuse on MT's transmission power and system spectral efficiency (SE) under different number of relays are also discussed in our work. Numerical results show that the proposed NC aware scheme can extend MTs' battery life at least 6% more than traditional method.

• Journal of Communications and Networks
• /
• 제18권4호
• /
• pp.629-638
• /
• 2016

In this paper, we investigate an energy-efficient resource allocation problem in a two-way relay (TWR) network consisting of multiple user pairs and an amplify-and-forward (AF) relay. As the users and relay have individual energy efficiencies (EE), we formulate a multi-objective optimization problem (MOOP). A single-objective optimization problem (SOOP) of the MOOP is introduced using a weighted-sum method, which achieves a single Pareto optimal point of the MOOP. To derive the algorithm for the SOOP, we propose a more tractable equivalent problem using the Karush-Kuhn-Tucker conditions of the SOOP, which guarantees convergence at the local optimal points. The proposed equivalent problem can be efficiently solved by the proposed iterative algorithm. Numerical results demonstrate the effectiveness of the proposed algorithm in achieving the optimal EE in multi-user AF TWR networks.

• 한국인터넷방송통신학회논문지
• /
• 제10권4호
• /
• pp.163-168
• /
• 2010

본 논문에서는 두 사용자가 서로의 정보만을 주고받는 기존의 다중 홉 양방향 중계 통신과는 다른 두 사용자가 두 목적지 노드로 신호를 전송하는 새로운 양방향 중계통신 기법을 제안한다. 또한 기존의 다중 홉 양방향 중계 통신에서는 각 노드가 수신신호에서 자신의 신호 성분을 제거하는 back-propagating self-interference 기법을 수행해야하며, 이로 인해 각 노드에서 신호처리 복잡도가 크게 증가하는 문제점이 있다. 이러한 문제점을 해결하기 위해 본 논문에서는 back-propagating self-interference 과정을 줄일 수 있는 Pre-cancellation 기법을 적용한다. 제안하는 기법이 기존의 다중 홉 양방향 중계 통신보다 우수한 성능을 보임을 시뮬레이션 결과로 보여주며, Pre-cancellation 기법의 사용 유무에 따른 시스템 복잡도와 성능간의 trade-off 관계를 분석한다.