• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권6호
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• pp.2282-2303
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• 2021

To solve the problems of heavy computing load and system transmission pressure in energy internet (EI), we establish a three-tier cloud-edge integrated EI network based on a cloud-edge collaborative computing to achieve the tradeoff between energy consumption and the system delay. A joint optimization problem for resource allocation and task offloading in the threetier cloud-edge integrated EI network is formulated to minimize the total system cost under the constraints of the task scheduling binary variables of each sensor node, the maximum uplink transmit power of each sensor node, the limited computation capability of the sensor node and the maximum computation resource of each edge server, which is a Mixed Integer Non-linear Programming (MINLP) problem. To solve the problem, we propose a joint task offloading and resource allocation algorithm (JTOARA), which is decomposed into three subproblems including the uplink transmission power allocation sub-problem, the computation resource allocation sub-problem, and the offloading scheme selection subproblem. Then, the power allocation of each sensor node is achieved by bisection search algorithm, which has a fast convergence. While the computation resource allocation is derived by line optimization method and convex optimization theory. Finally, to achieve the optimal task offloading, we propose a cloud-edge collaborative computation offloading schemes based on game theory and prove the existence of Nash Equilibrium. The simulation results demonstrate that our proposed algorithm can improve output performance as comparing with the conventional algorithms, and its performance is close to the that of the enumerative algorithm.

• 한국통신학회논문지
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• 제34권4A호
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• pp.316-323
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• 2009

본 논문은 셀간 간섭을 제어하여 셀 경계 사용자의 데이터 전송율을 증가시키는 기술인 소프트 주파수 재사용시 전력 할당에 관한 것이다. 소프트 주파수 재사용 기술은 셀 경계 사용자의 데이터 전송율을 개선하는데 유용한 기술이나 주파수 재사용 지수가 증가되어 셀 평균 데이터 전송율을 감소시키는 문제가 있다. 본 논문에서는 하나의 중앙 제어기가 물리적 거리가 인접한 여러 개의 셀을 제어하는 환경에서, 셀 경계 사용자의 데이터 전송율 개선하면서도 셀 평균 전송율 감소를 최소화하도록 소프트 주파수 재사용을 위한 송신 전력 할당 기법을 제안한다. 시스템 시뮬레이션을 통하여 인접한 두 셀에 소프트 주파수 재사용 기술을 적용하여 소프트 주파수 재사용에 의한 셀 평균 데이터 전송율 감소 정도와 제안하는 전력 할당 기법에 의한 셀 평균 데이터 전송을 개선을 살펴본다.

• 한국정보통신학회논문지
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• 제10권1호
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• pp.15-22
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• 2006

OFDMA 시스템에서 단말기는 기지국과 같이 최소 1개부터 최대일 때 부채널 전부를 사용할 수 있지만 단말기의 송신전력은 기지국보다 낮게 설계되기 때문에 부채널 전부를 사용할 수 있는 거리(FLR : full loading range)의 제한이 생기고 FLR 외부에 위치한 단말은 기존의 개방루프 전력제어 방식을 사용할 수 없는 문제가 발생한다. 본 논문에서는 OFDMA 시 스템의 ranging 정보를 이용하여 단말기의 위치를 파악하고 단말기의 위치에 따라서 사용가능한 부채널수를 제한하고 PCG(power concentration gain)를 인가하는 방식을 제안하였다. 시뮬레이션을 통한 실험 결과에서 제안된 방식은 단말기의 위치에 따라서 상향링크 무선자원의 최적 활용을 가능하게 하며 FLR 외부에서 개방루프 전력 제어가 별도의 하드웨어 없이 가능함을 확인하였다.

• 한국통신학회논문지
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• 제38A권7호
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• pp.571-579
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• 2013

본 논문은 셀룰러 네트워크에서 D2D (device-to-device) 통신을 고려한 시스템의 에너지 효율적인 모드 선택 기법 (mode selection) 및 파워 할당 기법 (power allocation)을 제안한다. 본 논문에서는 각 단말(device)의 에너지 효율성의 합 측면에서 에너지 효율성 (energy efficiency)을 분석한다. 먼저, 각 단말의 모든 가능한 모드에 대해 에너지 효율을 최대화하는 전송 파워를 계산한다. 제안하는 파워 할당 기법은 시스템 용량 측면에서 최적은 아니지만, 에너지 효율성 측면에서 최적의 성능을 보인다. 제안하는 전송 파워 할당 기법을 기반으로, 모든 가능한 모드에 대해 에너지 효율성을 구한다. 다음 단계로, 모든 가능한 모드 중에서 최대의 에너지 효율성을 갖는 모드를 구하며 동시에 해당 모드의 할당 전송 파워를 도출할 수 있다. 제안 기법은 에너지 효율성 측면에서 최적의 성능을 보이며, 기존 기법에 비해 월등한 성능을 보인다.

• 한국통신학회논문지
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• 제39B권2호
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• pp.61-74
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• 2014

In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5209-5228
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• 2016

Device-to-device (D2D) communication underlaying cellular networks can bring significate benefits for improving the performance of mobile services. However, it hinges on elaborate resource sharing scheme to coordinate interference between cellular users and D2D pairs. We formulate a joint mode selection, link allocation and power control optimization problem for D2D communication sharing uplink resources in a multi-user cellular network and consider the efficiency and the fairness simultaneously. Due to the non-convex difficulty, we propose a three-step scheme: firstly, we conduct mode selection for D2D pairs based on a minimum distance metric after an admission control and obtain some cellular candidates for them. And then, a cellular candidate will be paired to each D2D pair based on fairness. Finally, we use Lagrangian Algorithm to formulate a joint power control strategy for D2D pairs and their reused cellular users and a closed-form of solution is derived. Simulation results demonstrate that our proposed algorithms converge in a short time. Moreover, both the sum rate of D2D pairs and the energy efficiency of cellular users are improved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.3542-3566
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• 2018

In this paper, we investigate a buffer-aided wireless powered cooperative communication network (WPCCN), in which the source and relay harvest the energy from a dedicated power beacon via wireless energy transfer, then the source transmits the data to the destination through the relay. Both the source and relay are equipped with an energy buffer to store the harvested energy in the energy transfer stage. In addition, the relay is equipped with a data buffer and can temporarily store the received information. Considering the buffer-aided WPCCN, we propose two buffer-aided relaying protocols, which named as the buffer-aided harvest-then-transmit (HtT) protocol and the buffer-aided joint mode selection and power allocation (JMSPA) protocol, respectively. For the buffer-aided HtT protocol, the time-averaged achievable rate is obtained in closed form. For the buffer-aided JMSPA protocol, the optimal adaptive mode selection scheme and power allocation scheme, which jointly maximize the time-averaged throughput of system, are obtained by employing the Lyapunov optimization theory. Furthermore, we drive the theoretical bounds on the time-averaged achievable rate and time-averaged delay, then present the throughput-delay tradeoff achieved by the joint JMSPA protocol. Simulation results validate the throughput performance gain of the proposed buffer-aided relaying protocols and verify the theoretical analysis.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권1호
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• pp.319-333
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• 2022

In order to enhance system energy efficiency, bidirectional link resource allocation strategy in GFDM-based multiuser SWIPT systems is proposed. In the downlink channel, each SWIPT user applies power splitting (PS) receiver structure in information decoding (ID) and non-linear energy harvesting (EH). In the uplink channel, information transmission power is originated from the harvested energy. An optimization problem is constructed to maximize weighted sum ID achievable rates in the downlink and uplink channels via bidirectional link power allocation as well as subcarriers and subsymbols scheduling. To solve this non-convex optimization problem, Lagrange duality method, sub-gradient-based method and greedy algorithm are adopted respectively. Simulation results show that the proposed strategy is superior to the fixed subcarrier scheme regardless of the weighting coefficients. It is superior to the heuristic algorithm in larger weighting coefficients scenario.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4661-4680
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• 2016

Cognitive radio (CR) technology is an effective solution to the spectrum scarcity issue. Collaborative spectrum sensing is known as a promising technique to improve the performance of spectrum sensing in cognitive radio networks (CRNs). However, collaborative spectrum sensing is vulnerable to spectrum data falsification (SSDF) attack, where malicious users (MUs) may send false sensing data to mislead other secondary users (SUs) to make an incorrect decision about primary user (PUs) activity, which is one of the key adversaries to the performance of CRNs. In this paper, we propose a coalition based malicious users detection (CMD) algorithm to detect the malicious user in CRNs. The proposed CMD algorithm can efficiently detect MUs base on the Geary'C theory and be modeled as a coalition formation game. Specifically, SSDF attack is one of the key issues to affect the resource allocation process. Focusing on the security issues, in this paper, we analyze the power allocation problem with MUs, and propose MUs detection based power allocation (MPA) algorithm. The MPA algorithm is divided into two steps: the MUs detection step and the optimal power allocation step. Firstly, in the MUs detection step, by the CMD algorithm we can obtain the MUs detection probability and the energy consumption of MUs detection. Secondly, in the optimal power allocation step, we use the Lagrange dual decomposition method to obtain the optimal transmission power of each SU and achieve the maximum utility of the whole CRN. Numerical simulation results show that the proposed CMD and MPA scheme can achieve a considerable performance improvement in MUs detection and power allocation.

• International journal of advanced smart convergence
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• 제1권2호
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• pp.34-38
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• 2012

The recent increase in use of the IEEE 802.15.4 standard for wireless connectivity in personal area networks makes of it an important technology for low-cost low-power wireless personal area networks. Studies showed that voice communications over IEEE 802.15.4 networks is feasible by Guaranteed Time Slot (GTS) allocation; but there are some constraints to accommodate voice transmission beyond two hops due to the excessive transmission delay. In this paper, we propose a GTS allocation scheme for bidirectional voice traffic in IEEE 802.15.4 multihop networks with the goal of achieving fairness and optimization of resource allocation. The proposed scheme uses a greedy algorithm to allocate GTSs to devices for successful completion of voice transmission with efficient use of bandwidth while considering closest devices with another factor for starvation avoidance. We analyze and validate the proposed scheme in terms of fairness and resource optimization through numeral analysis.