• ETRI Journal
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• 제37권4호
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• pp.717-726
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• 2015

In this paper, we study an asymmetric two-way relaying network where two source nodes intend to exchange information with the help of multiple relay nodes. A hybrid time-division broadcast relaying scheme with joint relay selection (RS) and power allocation (PA) is proposed to realize energy-efficient transmission. Our scheme is based on the asymmetric level of the two source nodes' target signal-to-noise ratio indexes to minimize the total power consumed by the relay nodes. An optimization model with joint RS and PA is studied here to guarantee hybrid relaying transmissions. Next, with the aid of our proposed intelligent optimization algorithm, which combines a genetic algorithm and a simulated annealing algorithm, the formulated optimization model can be effectively solved. Theoretical analyses and numerical results verify that our proposed hybrid relaying scheme can substantially reduce the total power consumption of relays under a traffic asymmetric scenario; meanwhile, the proposed intelligent optimization algorithm can eventually converge to a better solution.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2949-2963
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• 2019

A novel distributed compress-and-forward (CF) system based on multi-relay network is presented. In this system, as the direct link between the source and destination is invalid due to some reasons, such as the limited power, special working environment, or even economic factors, relays are employed to receive analog signals and carry on distributed compressed encoding. Subsequently, the digital signals are transmitted to the destination via wireless channel. Moreover, a theoretical analysis for the system is provided by utilizing the Chief Executive Officer (CEO) theory and Shannon channel capacity theory, and the rate-distortion function as well as the connection between the transmission rate and the channel capacity are constructed. In addition, an optimal signal-to-noise ratio (SNR) -based power allocation method is proposed to maximize the quantization SNR under the limited total power. Simulation result shows that the proposed CF system outperforms the amplify-and-forward (AF) system versus the SNR performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1533-1546
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• 2013

Wireless multicast is considered as an effective transmission mode for the future mobile social contact services supported by Long Time Evolution (LTE). Though wireless multicast has an excellent resource efficiency, its performance suffers deterioration from the channel condition and wireless resource availability. Cognitive Radio (CR) and Device to Device (D2D) are two solutions to provide potential resource. However, resource allocation for cognitive wireless multicast based on D2D is still a great challenge for LTE social networks. In this paper, a joint sub-carriers and power allocation model based on D2D for general cognitive radio multicast (CR-D2D-MC) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) LTE systems. By opportunistically accessing the licensed spectrum, the maximized capacity for multiple cognitive multicast groups is achieved with the condition of the general scenario of imperfect spectrum sensing, the constrains of interference to primary users (PUs) and an upper-bound power of secondary users (SUs) acting as multicast source nodes. Furthermore, the fairness for multicast groups or unicast terminals is guaranteed by setting a lower-bound number of the subcarriers allocated to cognitive multicast groups. Lagrange duality algorithm is adopted to obtain the optimal solution to the proposed CR-D2D-MC model. The simulation results show that the proposed algorithm improves the performance of cognitive multicast groups and achieves a good balance between capacity and fairness.

• 한국인터넷방송통신학회논문지
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• 제13권5호
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• pp.65-70
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• 2013

본 논문에선, 정적 무선 네크워크에서 에너지 절약을 얻기 위한 멀티 홉 협력 전송 프로토콜을 제안한다. 네트워크의 각 터미널에서는 수신된 신호를 각 수신단에서 등 이득 결합 기법을 사용하고 단일 안테나를 설치한다. 또한, 각 구간에서 최적의 전체 전송 전력의 할당 방법을 제안한다. 몬테-카를로 시뮬레이션으로 평균 전체 전송 전력과 구간의 평균 수의 부분에서 멀티 홉 직접 전송(MDT)와 Khadani에 의해 제안된 협력 라우팅 프로토콜을 제안된 프로토콜로 성능을 비교 분석한다.

• 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.

• 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.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.422-424
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• 2002

Many methods about real power flow tracing have been suggested. Electric power industrials and organizations of the world use the method which is best suitable to themselves in practical aspects. In this paper we calculate the real power transfer between individual generators and loads referencing the method introduced by oversea's paper. It is considered to be significant to the wholesale competition market and transmission open access. Based on ac load flow solution and graph theory, the simulation on IEEE 30-bus system are carried out and the results are compared with that of oversea's paper. Also the simulation on the power system of Korea is carried out and the results are analyzed.

• Journal of Information Processing Systems
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• 제10권3호
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• pp.459-470
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• 2014

In this paper, the average probability of the symbol error rate (SER) and throughput are studied in the presence of joint spectrum sensing and data transmission in a cognitive relay network, which is in the environment of an optimal power allocation strategy. In this investigation, the main component in calculating the secondary throughput is the inclusion of the spatial false alarms, in addition to the conventional false alarms. It has been shown that there exists an optimal secondary power amplification factor at which the probability of SER has a minimum value, whereas the throughput has a maximum value. We performed a Monte-Carlo simulation to validate the analytical results.

• 한국멀티미디어학회논문지
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• 제3권6호
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• pp.625-632
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• 2000

차세대 대용량 멀티미디어 무선통신시스템의 실현 및 주파수의 효율적 이용을 위해 불가결한 멀티 마이크로 셀 환경 하에서의 효율적인 시스템 구성을 위해서는 정보의 종류 및 트래픽의 시간적인 변동에 대해서 유연한 액세스 제어가 필요하다. 본 논문에서는 높은 시스템 용량을 실현하기 위해, 송신 단말의 평균 CNR(반송파 전력대 잡음 전력비)에 대응하여 변조 파라미터를 동적으로 설정하는 저속적응변조방식과 트래픽 상황에 대응하여 TDMA 데이터 슬롯 수를 가변으로 하는 멀티 슬롯 할당 방식을 조합시켰다. 적응 멀티 슬롯 할당 방식을 제안하고, 제안방식의 평균 메시지 지연 특성을 시뮬레이션에 의해 평가한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3876-3895
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• 2014

Recently, Heterogeneous Network (HetNet) with Coordinated Multi-Point (CoMP) scheme is introduced into Long Term Evolution-Advanced (LTE-A) systems to improve digital services for User Equipments (UEs), especially for cell-edge UEs. However, Radio Resource Management (RRM), including Resource Block (RB) scheduling and Power Allocation (PA), in this scenario becomes challenging, due to the intercell cooperation. In this paper, we investigate the RRM problem for downlink transmission of HetNet system with Joint Processing (JP) CoMP (both joint transmission and dynamic cell selection schemes), aiming at maximizing weighted sum data rate under the constraints of both transmission power and backhaul capacity. First, joint RB scheduling and PA problem is formulated as a constrained Mixed Integer Programming (MIP) which is NP-hard. To simplify the formulation problem, we decompose it into two problems of RB scheduling and PA. For RB scheduling, we propose an algorithm with less computational complexity to achieve a suboptimal solution. Then, according to the obtained scheduling results, we present an iterative Karush-Kuhn-Tucker (KKT) method to solve the PA problem. Extensive simulations are conducted to verify the effectiveness and efficiency of the proposed algorithms. Two kinds of JP CoMP schemes are compared with a non-CoMP greedy scheme (max capacity scheme). Simulation results prove that the CoMP schemes with the proposed RRM algorithms dramatically enhance data rate of cell-edge UEs, thereby improving UEs' fairness of data rate. Also, it is shown that the proposed PA algorithms can decrease power consumption of transmission antennas without loss of transmission performance.