Earticle

본 논문에서는 다중 홉 시스템에서 하나의 홉에 대한 채널 정보만을 이용하는 효율적인 부분 중계 노드 선택(efficient partial relay selection, EPRS) 기법에 대한 아웃티지 확률을 레일레이 페이딩 채널에서 분석한다. 특히, 디코딩 후 전달 중계 기반의 EPRS 기법에 대한 정확한 아웃티지 확률의 식을 유도한다. 또한, 다중 홉 시스템에서 EPRS 기법의 실효성을 확인하기 위하여, 임의의 중계 경로에서 종단간 신호 대 잡음비와 각 홉의 신호 대 잡음비의 상관관계를 분석한다. 그리고, 수치적 결과를 통해 EPRS 기법과 모든 채널 정보를 이용하는 중계 노드 선택 기법의 아웃티지 성능을 비교한다.

In this paper, the outage probability of efficient partial relay selection(EPRS) using only one-hop channel information in multi-hop systems is analyzed in Rayleigh fading channels. In particular, we derive an exact and closed-form expression for the outage probability of decode-and-forward relaying based EPRS. In order to prove the usefulness of EPRS in multi-hop systems, we also analyze the correlation between the end-to-end signal-to-noise ratio(SNR) and the SNR for each hop at an arbitrary relaying path. Furthermore, through numerical investigation, we compare the outage performances for EPRS and the best relay selection using all channel information.

본 논문에서는 전체 채널 정보와 부분 채널 정보를 이용하여 중계 노드를 선택하는 각각의 증폭 후 전달 중계 시스템을 고려한다. 여기서, 소스 노드와 목적지 노드간의 직접 통신 링크를 고려한다. 그리고, 전체 채널 정보와 부분 채널 정보를 이용하여 중계 노드를 선택하는 각각의 증폭 후 전달 중계 시스템에 대한 아웃티지 확률을 레일레이 페이딩 채널을 가정하여 분석한다. 특히, 각각의 시스템에 대하여 정확한 아웃티지 확률과 아웃티지 확률의 하한, 그리고 점근적인 아웃티지 확률 식들을 유도한다. 또한, 전체 채널 정보와 부분 채널 정보를 이용하여 중계 노드를 선택하는 각각의 증폭 후 전달 중계 시스템에 대하여 얻을 수 있는 코딩 이득을 제시한다. 수치적 결과를 통해, 모든 분석 표현식들을 검증하고, 첫 번째와 두 번째 홉의 평균 채널 전력이 상이한 경우와 중계 노드의 수가 상이한 경우에 대하여 각각의 시스템에 대한 코딩 이득을 비교한다.

In this paper, we consider the amplify-and-forward relaying systems with the relay selection (AF-RS) using full channel information (FCI) and using partial channel information (PCI), respectively, in which the direct communication link between a source and a destination is available. And, the outage probabilities for the AF-RS using FCI and using PCI are investigated in Rayleigh fading channels, respectively. We provide exact outage probabilities, tight outage probability lower bounds, and asymptotic outage probabilities, respectively. And also, we present coding gains achievable by the AF-RS using FCI and using PCI. Through numerical investigation, all the analytic expressions are verified, and the coding gains are respectively evaluated with different average channel powers for the first and the second hop as well as different numbers of relays.

듀얼 홉 중계 시스템에서 기존의 부분 중계 노드 선택 기법은 첫 번째 홉에 대한 채널 정보만을 이용하여 중계 노드를 선택한다. 반면에, 효율적인 부분 중계 노드 선택 기법은 종단간 링크 품질과 두 홉 중 평균 채널 전력이 작은 홉에 대한 링크 품질과의 상관 계수가 다른 홉에 대한 링크 품질과의 상관 계수 보다 큼을 이용하여 각각의 중계 노드에 대한 종단간 링크에서 첫 번째 홉과 두 번째 홉 중 평균 채널 전력이 작은 홉에 대한 채널 정보를 이용하여 중계 노드를 선택한다. 본 논문에서는 듀얼 홉 디코딩 후 전달 중계 시스템에서 기존의 부분 중계 노드 선택 기법 및 효율적인 부분 중계 노드 선택 기법에 대한 아웃티지 확률을 비균일 분포를 갖는 레일레이 페이딩 채널 하에서 분석한다. 또한, 수치적 결과를 통해 효율적인 부분 중계 노드 선택 기법, 기존의 부분 중계 노드 선택 기법, 두 홉에 대한 모든 채널 정보를 이용하는 중계 노드 선택 기법의 아웃티지 성능을 비교한다.

In dual-hop relaying systems, the conventional partial relay selection is based on the channel information only for the first hop. On the other hand, the efficient partial relay selection is based on the channel information for the hop with the minimum of the average channel powers for the first and second hops at each end-to-end link since the correlation coefficient between the end-to-end link quality and the link quality of the hop with the minimum of the average channel powers for the first and second hops is larger than that between the end-to-end link quality and the link quality of the other hop. In this paper, the outage probability of the conventional partial relay selection and the efficient partial relay selection in dual-hop decode-and-forward relaying systems is analyzed for non-identically distributed Rayleigh fading channels. Through numerical investigation, the outage performance of the efficient partial relay selection is compared with the outage performances of the conventional partial relay selection and the best relay selection based on all the channel information for the first and second hops.

In this paper, we derive the outage probability for M-ary phase shifting keying (MPSK) and M-ary quadrature amplitude modulation (MQAM) burst transmission (BT) of adaptive decode-and-forward (ADF) cooperative relay systems over quasi-static Rayleigh fading channels. Within a burst, there are pilot symbols and data symbols. Pilot symbols are used for channel estimation schemes and each relay node's transmission mode selection schemes. At first, we focus on ADF relay systems in which the probability density function (PDF) is derived on the basis of error events at relay nodes corresponding to channel estimation errors. Next, the average outage probability is derived as an approximate expression for an arbitrary link signal-to-noise ratio (SNR) for different modulation orders. Its accuracy is demonstrated by comparison with simulation results. Further, it is confirmed that BT-ADF relay systems with pilot symbol based channel estimation schemes enables to select correctly decoded relay nodes without additional signaling between relay nodes and the destination node, and it is verified that the ideal performance is achieved with small SNR loss.

This paper studies physical layer security for Alamouti space?time block code (STBC) with joint maximum likelihood (JML) or zero forcing (ZF) detection techniques particularly over multi-input single-output (MISO) wiretap time-selective Rayleigh fading channels. Specifically, we derive the secrecy outage probabilities (SOPs) and their concise but effective approximations for various combinations of JML and ZF at the legitimate receiver and eavesdropper. We also investigate the secrecy diversity gain by applying the high signal-to-noise ratio (SNR) approximation of SOP and prove that the corresponding asymptotic diversity order of two, two, one, and one can be achieved for JML-JML, JML-ZF, ZF-JML, and ZF-ZF, respectively. Our asymptotic analytical results corroborate that the secrecy diversity order is dominantly affected by the detection strategy of the legitimate receiver rather than that of the eavesdropper.

The rise of wireless devices makes interference a key challenge for reliable communication in dense spectrum-sharing networks. This paper proposes a graph neural network (GNN)-based power control algorithm to minimize the worst-case outage probability by using statistical channel state information (CSI), i.e., position information. By representing the network as a fully connected directed graph with node and edge features derived from transceiver positions, the GNN employs message-passing layers to aggregate interference patterns and infer near-optimal transmit powers. Simulation results demonstrate the scalability and generalization capability of the proposed method, confirming its suitability for real-time deployment in large-scale wireless systems.

In this paper, we propose a new design metric called modified outage probability (MOP) for protograph-based low-density parity-check (LDPC) codes over the uncorrelated Rayleigh fading channel. In contrast to the conventional threshold metric, the MOP predicts the frame error rate (FER) performance accurately over the fading channel. Based on MOPs, we optimize protograph-based LDPC codes while considering the trade-off between accuracy and computational complexity. It is shown that the optimized LDPC codes outperform the conventional threshold-based LDPC codes at the FER of for the both medium and high code-rate regions.

우리나라에서는 재난안전통신망(PS-LTE) 주파수로 철도망(LTE-R)에 이미 지정되어 있는 700 MHz 대역이 할당되었다. 따라서 동일채널간섭으로 인한 아웃티지를 줄이고 수율을 높이기 위한 연구가 필요하다. 본고에서는 안전망과 철도망이 공존하는 LTE-R 네트워크 다운링크 환경에서 RAN 공유시와 비 RAN 공유시, 또한 협력통신(CoMP)을 적용시와 미적용시에 PS-LTE UE 수율의 향상과 LTE-R UE 아웃티지 감소를 비교 분석한다. PS-LTE 와 LTE-R 네트워크의 공존 시나리오를 수행방법에 기반하여 네가지로 구분하고, 각각의 시나리오별로 UE의 아웃티지와 평균 수율을 측정한다. 열차제어신호는 최상위 MCS (mission critical service)에 해당되기에, PS-LTE UEs가 LTE-R 네트워크의 RAN 공유시, LTE-R UE에 더 높은 우선권을 주어 자원을 할당한다. RAN 공유 환경에서 협력통신인 CS CoMP를 적용하는 경우, 최고의 수율과 최소의 UE 아웃티지 성능을 보임을 알 수 있다.

In the Republic of Korea, the LTE-based public safety (PS-LTE) network is being built for the 700 MHz frequency band. However, the same bands are also assigned to the LTE-based high-speed railway (LTE-R) network. Therefore, it is essential to utilize the co-channel interference management schemes for the coexistence of two LTE networks in order to increase the system throughput and to reduce the user outage probability. In this paper, we focus on the downlink (DL) system for the coexistence of PS-LTE and LTE-R networks by considering non radio access network (RAN) sharing and LTE-R RAN sharing by PS-LTE users (UEs) to analyze the UE throughput. Moreover, we also utilize the cooperative communications schemes, such as coordinated multipoint (CoMP) for the coexistence of PS-LTE and LTE-R networks in order to reduce the UE outage probability. We categorize the coexistence of PS-LTE and LTE-R networks into four different scenarios, and evaluate the performance of each scenario by the important performance indexes, such as UE average throughput and UE outage probability.

Based on variable-gain amplify-and-forward (VAF) relaying scheme, the lower bound on outage probability (OP) of the mobile-relay-based mobile-to-mobile (M2M) networks over N-Nakagami fading channels is investigated in this paper. By the method of the harmonic mean of positive random variables, the exact closed form expression of the lower bound on OP is derived. Then the OP performance under different conditions is evaluated through numerical simulations. The numerical simulation results coincide with the theoretical results well, and the accuracy of the analytical results is verified. The simulation results showed that: the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power-allocation parameter have an important influence on the OP performance.

In this paper, we propose the analytical approach for burst transmission (BT) adaptive decode-and-forward (ADF) relaying schemes consisting of burst transmission over quasi-static Rayleigh fading channels. At first, we focus on the error-event at relay nodes for symbol burst transmission, whereas previous researches considered one data symbol transmission so that they showed the best performance bounds. By considering symbol burst for ADF relay systems, we derive an exact outage probability expression which can be the performance of practical systems. Furthermore, the average outage probability is derived in approximated closed-form upper bound for an arbitrary link SNR. The derived analytical approach is verified based on the number of relays and burst symbols. Its accuracy is confirmed by comparison with simulation results.

본 논문에서는 복호 후 재전송 기반의 중계기 시스템에서 재머를 사용했을 때의 보안 불능 확률을 연구한다. 물리 계층에서 보안 용량을 증가시키기 위해서 선택되지 않은 중계기들 중에서 재머를 선택하여 의도적인 잡음을 발생시키도록 할 수 있다. 재머에 의한 잡음은 수신자와 도청자에서 동일하게 간섭으로 작용하지만 송신자-도청자 링크 간의 채널 품질을 송시자-수신자 링크의 채널보다 더 악화 시키는 최적의 재머를 선택하여 물리 계층 보안을 강화할 수 있다. 본 논문에서는 재머의 유무에 따른 보안 불능 확률의 이론적인 식을 계산하고, 그 식이 타당한지 증명하기 위하여 이론값과 모의실험을 통한 실험값을 비교해 본다.

In this paper, we study the secrecy outage probability when using jammer in a relay system based on decode-and-forward. The jammer may be selected among the relays not selected to increase the security capacity in the physical layer so as to generate intentional noise. Jammer noise can equally interfere with the receiver and eavesdropper but can enhance the physical layer security by selecting an optimal jammer that makes the channel quality between the sender-eavesdropper links worse than the channel of the sender-receiver link. In this paper, we compute the theoretical formula of the secrecy outage probability with and without jammers, and compare the theoretical value with the simulation value to prove that the equation is valid.

본 논문에서는 복호 후 재전송 기반의 중계기 시스템에서 협력 다이버시티와 재머를 사용했을 때의 보안 불 능 확률을 연구한다. 협력 다이버시티를 얻기 위해서 수신자와 도청자에서 MRC 기법을 사용한다. MRC 기법을 사용 하기 위해서 송신자와 수신자, 송신자와 도청자 사이의 직접 링크를 사용한다. 보안용량을 증가시키기 위해서 의도적인 잡음 신호를 발생 시키는 재머를 사용한다. 재머는 의도적인 잡음을 발생시켜 도청자의 채널 품질을 떨어뜨리고 물리 계층 보안이 실현될 수 있도록 돕는다. 보안 성능을 평가하기 위해서 보안 불능 확률이 사용된다. 시스템은 레일리 페 이딩 채널 하에 있다고 가정한다.

In this paper, we study the secrecy outage probability when using cooperative diversity and jammer in a relay system based on decode-and-forward. MRC method is used in receiver and eavesdroppers to obtain cooperative diversity. To use the MRC technique, direct links between the sender and receiver, and between the sender and the eavesdropper are used, respectively. Jammers are used to generate intentional noise siganls to increase security capacity. Jammers generate intentional noise, degrading the channel quality of the eavesdropper and helping physical layer security be realized. The secrecy outage probability is used to evaluate security performance. Assume that the system is under the Rayleigh fading channel.

Recently, the issue of excessive energy consumption in wireless communications has become increasing critical, and the energy harvesting as a renewable energy resource, has received extensive attractions. In this paper, a wireless sensor network (WSN) is considered, where the source-destination pair communicates via an energy harvesting relay links. We study the problem of the harvested energy distribution among the source, relay and destination nodes. An effective power allocation scheme is developed which exploits the decode-and-forward (DF) relaying strategy and channel state information. The outage probability is analyzed and simulation results show that the outage performance for two sub-channels is always performs well in the cases of different threshold target data rate. Moreover, the effect of the different radio of the optimal sub-channel gain and Rayleigh channel gain on the outage performance is evaluated.

In this letter, we propose a novel two-way amplify- and-forward (AF) relay selection scheme over independent flat Nakagami-m fading channels. In the proposed schemes, two users first sequentially broadcast their respective information to all the relays. Then, the Nth best-relay perform AF protocol on the received signals sent from the two users and forward them to both users. The Nth best-relay is selected to optimize the end-to- end performance of the system transmission. The performance of the proposed system is quantified by deriving the lower bound of the overall outage probability and average symbol error rate (SER). The effectiveness of our proposed selection scheme and analytical results is verified by simulations.

In cellular networks, the application of device-to-device (D2D) technology can effectively improve the system spectral efficiency. In order to research the performance of D2D communication in multi-cell cellular system, this paper proposed a dynamic power control algorithm based on interference restricted area to solve the interference problem between D2D communication and cellular communication in multi-cell. First we use Laplace Transform to analyze the interference, then based on the analyze of outage probability and area spectral efficiency, through system-level simulation, research the impact of D2D user equipment density, D2D communication distance and different interference restricted area sizes on outage probability and area spectral efficiency. Simulation results show that interference restricted area can effectively reduce communication outage probability, as well as improve system area spectral efficiency.

The average symbol error probability (ASEP) and outage probability (OP) performance of the switched diversity combining (SDC) system over N-Nakagami fading channels is investigated in this paper. The probability density function (PDF) of the signal-to-noise ratio (SNR) is used to derive exact and approximate ASEP expressions for phase shift keying (PSK) and pulse amplitude modulation (PAM). Exact closed-form expressions for OP of the SDC system are also presented. The ASEP and OP performance under different conditions is evaluated through numerical simulation to verify the analysis. Results are presented which show that the performance of the SDC system is improved when the number of diversity branches and the fading coefficient is increased, but is degraded as the number of cascaded components is increased.

The outage probability (OP) and average symbol error probability (ASEP) performance of multiple-mobile-relay-based mobile-to-mobile (M2M) networks with decode-and-forward (DF) relaying over N-Nakagami fading channels is investigated in this paper. The power allocation problem is formulated to determine how the overall transmit power should be shared between broadcasting and relaying phases for performance optimization. Then the OP and ASEP performance under different conditions is evaluated through numerical simulations to verify the analysis. The simulation results show that the fading coefficient, the number of cascaded components, the relative geometrical gain, the power-allocation parameter, and the number of mobile relays have an important influence on the OP and ASEP performance.

In order to achieve the balance between implementation complexity and system performance, a new hybrid combining technique named SEC-SC is proposed in this paper, which is composed of switch-and-examine combining (SEC) and selection combining(SC).The average symbol error probability (ASEP) and outage probability (OP) of the SEC-SC system over N-Nakagami fading channels is investigated. The exact ASEP expressions are derived for several modulation schemes, including phase shift keying (PSK), quadrature amplitude modulation (QAM), and pulse amplitude modulation (PAM). The exact closed-form OP expressions are also presented. Then the ASEP and OP performance under different conditions is evaluated through numerical simulations to verify the analysis. The simulation results showed that the performance of the SEC-SC system is improved with the diversity branches and the fading coefficient increased, but the level of improvement is declined as the number of cascaded components increased.

The exact closed-form outage probability (OP) expressions of the multiple-mobile-relay-based mobile-to-mobile (M2M) cooperative networks over N-Nakagami fading channels are derived for selection incremental relaying (SIR). Then the OP performance under different conditions is evaluated through numerical simulations. The numerical simulation results coincide with the theoretical results well, and the accuracy of the analytical results is verified. The simulation results showed that: the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power-allocation parameter have an important influence on the OP performance.

Based on decode-and-forward (DF) relaying scheme, the exact closed-form expression of the outage probability (OP) for the home mobile-to-mobile (M2M) cooperative networks over N-Nakagami fading channels is derived in this paper. Then the OP performance under different conditions is evaluated through numerical simulations. The numerical simulation results coincide with the theoretical results well, and the accuracy of the theoretical results is verified. The simulation results showed that: the fading coefficient, the number of cascaded components, the relative geometrical gain, and the power-allocation parameter have an important influence on the OP performance.