• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4848-4863
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• 2016

The explosive wireless data service requirement accompanied with carbon dioxide emission and consumption of traditional energy has put pressure on both industria and academia. Wireless networks powered with the uneven and intermittent generated renewable energy have been widely researched and lead to a new research paradigm called green communication. In this paper, we comprehensively consider the total generated renewable energy, QoS requirement and channel quality, then propose a utility based renewable energy allocation policy. The utility here means the satisfaction degree of users with a certain amount allocated renewable energy. The energy allocation problem is formulated as a constraint optimization problem and a heuristic algorithm with low complexity is derived to solve the raised problem. Numerical results show that the renewable energy allocation policy is applicable not only to soft QoS, but also to hard QoS and best effort QoS. When the renewable energy is very scarce, only users with good channel quality can achieve allocated energy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4145-4164
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• 2016

Energy harvesting is an increasingly attractive source of power for cellular networks, and can be a promising solution for green networks. In this paper, we consider a cellular network with power beacons powering multiple mobile terminals with microwave power transfer in energy beamforming. In this network, the power beacons are powered by grid and renewable energy jointly. We adopt a dual-level control architecture, in which controllers collect information for a core controller, and the core controller has a real-time global view of the network. By implementing the water filling optimized power allocation strategy, the core controller optimizes the energy allocation among mobile terminals within the same cluster. In the proposed green energy cooperation paradigm, power beacons dynamically share their renewable energy by locally injecting/drawing renewable energy into/from other power beacons via the core controller. Then, we propose a new water filling optimized green energy cooperation management strategy, which jointly exploits water filling optimized power allocation strategy and green energy cooperation in cellular networks. Finally, we validate our works by simulations and show that the proposed water filling optimized green energy cooperation management strategy can achieve about 10% gains of MT's average rate and about 20% reduction of on-grid energy consumption.

• 정보보호학회논문지
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• 제23권2호
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• pp.169-179
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• 2013

최근 스마트 폰, 스마트 패드와 같은 모바일 디바이스의 발전과 무선 네트워크 및 이동통신 네트워크의 발전으로 모바일 디바이스를 이용하는 서비스는 증가하고 있다. 그러나 무선 네트워크는 유선 네트워크에 비해 보안에 취약하므로 보다 강한 보안의 적용이 필요한 반면 배터리 기반의 모바일 디바이스는 낮은 계산 능력과 메모리 공간의 제약 및 무선통신에 사용되는 비용이 높기 때문에 보안의 적용은 효율적이어야 한다. 따라서 본 논문에서는 모바일 디바이스를 이용한 서비스에서 요구되는 보안 요구사항을 충족시키고 모바일 환경에 적합한 티켓 기반의 인증 기법을 제안한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.5149-5167
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• 2017

Reducing energy consumption in a wireless video sensor network (WVSN) is a crucial problem because of the high video data volume and severe energy constraints of battery-powered WVSN nodes. In this paper, we present an adaptive dynamic resizing approach for a SRAM communication buffer in a WVSN node in order to reduce the energy consumption and thereby, to maximize the lifetime of the WVSN nodes. To reduce the power consumption of the communication part, which is typically the most energy-consuming component in the WVSN nodes, the radio needs to remain turned off during the data buffer-filling period as well as idle period. As the radio ON/OFF transition incurs extra energy consumption, we need to reduce the ON/OFF transition frequency, which requires a large-sized buffer. However, a large-sized SRAM buffer results in more energy consumption because SRAM power consumption is proportional to the memory size. We can dynamically adjust any active buffer memory size by utilizing a power-gating technique to reflect the optimal control on the buffer size. This paper aims at finding the optimal buffer size, based on the trade-off between the respective energy consumption ratios of the communication buffer and the radio part, respectively. We derive a formula showing the relationship between control variables, including active buffer size and total energy consumption, to mathematically determine the optimal buffer size for any given conditions to minimize total energy consumption. Simulation results show that the overall energy reduction, using our approach, is up to 40.48% (26.96% on average) compared to the conventional wireless communication scheme. In addition, the lifetime of the WVSN node has been extended by 22.17% on average, compared to the existing approaches.

• Smart Structures and Systems
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• 제6권3호
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• pp.263-275
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• 2010

In the last decade, wireless sensor networks have emerged as a promising technology that could accelerate progress in the field of structural monitoring. The main advantages of wireless sensor networks compared to conventional monitoring technologies are fast deployment, small interference with the surroundings, self-organization, flexibility and scalability. These features could enable mass application of monitoring systems, even on smaller structures. However, since wireless sensor network nodes are battery powered and data communication is the most energy consuming task, transferring all the acquired raw data through the network would dramatically limit system lifetime. Hence, data reduction has to be achieved at the node level in order to meet the system lifetime requirements of real life applications. The objective of this paper is to discuss some general aspects of data processing and management in monitoring systems based on wireless sensor networks, to present a prototype monitoring system for civil engineering structures, and to illustrate long-term field test results.

• 한국위성정보통신학회논문지
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• 제12권3호
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• pp.98-102
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• 2017

이 논문에서는 백스케터 통신에 기반한 무선 센서인 보조 사용자의 성능을 향상시키기 위해 인지 무선 기반 백스케터 네트워크를 연구한다. 제안 된 모델에서, 캐리어 이미터를 추가하고 스펙트럼 센싱 정보를 활용하기 위해 이중감쇄를 피하는 것을 고려한다. 기본 채널이 사용 중일 때 보조 사용자는 Hybrid-Access Point(H-AP)와 캐리어 이미터를 통해 채널에서 RF 에너지를 수집 할 수 있다. 채널이 유휴 상태가 되면 보조 사용자는 수확된 에너지를 사용하여 무선 센서를 작동시키고 스펙트럼 센싱 후, 캐리어 이미터를 통해 백스케터 통신을 수행한다. 따라서 우리는 다수의 태그가 존재하는 벡스케터 채널을 deterministic과 멀티소스 요소로 수학적 모델링한다. 제안한 통신 환경에서 WiFi 신호를 활용한 벡스케터 통신의 BER 성능을 보인다.

• Journal of Communications and Networks
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• 제14권2호
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• pp.130-139
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• 2012

Energy harvesting has emerged as a powerful technology for complementing current battery-powered communication systems in order to extend their lifetime. In this paper a general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment. Assuming that the energy arrival process is known non-causally at the transmitter, the structure of the optimal transmission scheme, which maximizes the amount of transmitted data by a given deadline, is identified. Our framework includes models with continuous energy arrival as well as battery constraints. A battery that suffers from energy leakage is studied further, and the optimal transmission scheme is characterized for a constant leakage rate.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.114.6-114
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• 2001

According to expansion of wireless communication system and mobile device, interest has been growing in personal navigation system integrated with wireless system. In portable consumer electronics, such as cellular phones, GPS and PDA, one of major design factors is the power consumption. Solutions of reducing the power dissipation are low voltage, low system clock power management and so on. This paper develops a GPS receiver based on the advanced power management algorithm that achieves very low average power consumption. Both RF and DSP chips are powered down and reactivated only when the position fixing is required. In order to run, the developed includes the RTC calibration function and the fast reacquisition function using XMC (eXtended Multiple Correlator) ...

• Smart Structures and Systems
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• 제6권5_6호
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• pp.641-659
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• 2010

Structural Health Monitoring (SHM) gradually becomes a technique for ensuring the health and safety of civil infrastructures and is also an important approach for the research of the damage accumulation and disaster evolving characteristics of civil infrastructures. It is attracting prodigious research interests and the active development interests of scientists and engineers because a great number of civil infrastructures are planned and built every year in mainland China. In a SHM system the sheer number of accompanying wires, fiber optic cables, and other physical transmission medium is usually prohibitive, particularly for such structures as offshore platforms and long-span structures. Fortunately, with recent advances in technologies in sensing, wireless communication, and micro electro mechanical systems (MEMS), wireless sensor technique has been developing rapidly and is being used gradually in the SHM of civil engineering structures. In this paper, some recent advances in the research, development, and implementation of wireless sensors for the SHM of civil infrastructures in mainland China, especially in Dalian University of Technology (DUT) and Harbin Institute of Technology (HIT), are introduced. Firstly, a kind of wireless digital acceleration sensors for structural global monitoring is designed and validated in an offshore structure model. Secondly, wireless inclination sensor systems based on Frequency-hopping techniques are developed and applied successfully to swing monitoring of large-scale hook structures. Thirdly, wireless acquisition systems integrating with different sensing materials, such as Polyvinylidene Fluoride(PVDF), strain gauge, piezoresistive stress/strain sensors fabricated by using the nickel powder-filled cement-based composite, are proposed for structural local monitoring, and validating the characteristics of the above materials. Finally, solutions to the key problem of finite energy for wireless sensors networks are discussed, with future works also being introduced, for example, the wireless sensor networks powered by corrosion signal for corrosion monitoring and rapid diagnosis for large structures.

• 한국정보통신학회논문지
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• 제22권1호
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• pp.175-182
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• 2018

단말의 수가 증가하고 사물 인터넷 환경이 분산화 됨에 따라 랜덤 접속 기반의 무선전력 통신 네트워크에 관한 연구가 필요하다. 랜덤 접속 기반 무선전력 통신 네트워크에서 단말은 주어진 프레임 내에서 늦게 접속할수록 전송 전에 더 많은 에너지를 하베스팅하여 더 높은 파워로 송신할 수 있기 때문에 접속 성공시 더 높은 처리율을 얻을 수 있다. 이러한 특성에 기반하여 제안하는 랜덤 접속 제어 프로토콜은 채널 값에 따라 단말에게 우선순위를 부여하고 우선순위에 따라 랜덤 슬롯을 구분함으로써 접속점과의 근거리 단말이 원거리 단말보다 먼저 접속하게 만든다. 이를 통하여 근거리 단말의 처리율을 낮추고 원거리 단말의 처리율을 높이는 방식으로 이중 원근 문제를 완화시키고 사용자 공평성을 향상시킨다. 수학적 분석 및 모의실험 결과 제안 접속 제어 방식은 우선순위 레벨에 따라 채널 처리율 및 사용자 공평성 성능을 향상시킨다.